Adding upstream version 2.2.0.upstream/2.2.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

68 files changed, 5287 insertions, 0 deletions

diff --git a/pre_commit/__init__.py b/pre_commit/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/pre_commit/__init__.py
diff --git a/pre_commit/__main__.py b/pre_commit/__main__.py
new file mode 100644
index 0000000..5414068
--- /dev/null
+++ b/pre_commit/__main__.py
@@ -0,0 +1,5 @@
+from pre_commit.main import main
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/clientlib.py b/pre_commit/clientlib.py
new file mode 100644
index 0000000..56ec0dd
--- /dev/null
+++ b/pre_commit/clientlib.py
@@ -0,0 +1,317 @@
+import argparse
+import functools
+import logging
+import shlex
+import sys
+from typing import Any
+from typing import Dict
+from typing import Optional
+from typing import Sequence
+
+import cfgv
+from identify.identify import ALL_TAGS
+
+import pre_commit.constants as C
+from pre_commit.error_handler import FatalError
+from pre_commit.languages.all import all_languages
+from pre_commit.util import parse_version
+from pre_commit.util import yaml_load
+
+logger = logging.getLogger('pre_commit')
+
+check_string_regex = cfgv.check_and(cfgv.check_string, cfgv.check_regex)
+
+
+def check_type_tag(tag: str) -> None:
+    if tag not in ALL_TAGS:
+        raise cfgv.ValidationError(
+            f'Type tag {tag!r} is not recognized.  '
+            f'Try upgrading identify and pre-commit?',
+        )
+
+
+def check_min_version(version: str) -> None:
+    if parse_version(version) > parse_version(C.VERSION):
+        raise cfgv.ValidationError(
+            f'pre-commit version {version} is required but version '
+            f'{C.VERSION} is installed.  '
+            f'Perhaps run `pip install --upgrade pre-commit`.',
+        )
+
+
+def _make_argparser(filenames_help: str) -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help=filenames_help)
+    parser.add_argument('-V', '--version', action='version', version=C.VERSION)
+    return parser
+
+
+MANIFEST_HOOK_DICT = cfgv.Map(
+    'Hook', 'id',
+
+    cfgv.Required('id', cfgv.check_string),
+    cfgv.Required('name', cfgv.check_string),
+    cfgv.Required('entry', cfgv.check_string),
+    cfgv.Required('language', cfgv.check_one_of(all_languages)),
+    cfgv.Optional('alias', cfgv.check_string, ''),
+
+    cfgv.Optional('files', check_string_regex, ''),
+    cfgv.Optional('exclude', check_string_regex, '^$'),
+    cfgv.Optional('types', cfgv.check_array(check_type_tag), ['file']),
+    cfgv.Optional('exclude_types', cfgv.check_array(check_type_tag), []),
+
+    cfgv.Optional(
+        'additional_dependencies', cfgv.check_array(cfgv.check_string), [],
+    ),
+    cfgv.Optional('args', cfgv.check_array(cfgv.check_string), []),
+    cfgv.Optional('always_run', cfgv.check_bool, False),
+    cfgv.Optional('pass_filenames', cfgv.check_bool, True),
+    cfgv.Optional('description', cfgv.check_string, ''),
+    cfgv.Optional('language_version', cfgv.check_string, C.DEFAULT),
+    cfgv.Optional('log_file', cfgv.check_string, ''),
+    cfgv.Optional('minimum_pre_commit_version', cfgv.check_string, '0'),
+    cfgv.Optional('require_serial', cfgv.check_bool, False),
+    cfgv.Optional('stages', cfgv.check_array(cfgv.check_one_of(C.STAGES)), []),
+    cfgv.Optional('verbose', cfgv.check_bool, False),
+)
+MANIFEST_SCHEMA = cfgv.Array(MANIFEST_HOOK_DICT)
+
+
+class InvalidManifestError(FatalError):
+    pass
+
+
+load_manifest = functools.partial(
+    cfgv.load_from_filename,
+    schema=MANIFEST_SCHEMA,
+    load_strategy=yaml_load,
+    exc_tp=InvalidManifestError,
+)
+
+
+def validate_manifest_main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = _make_argparser('Manifest filenames.')
+    args = parser.parse_args(argv)
+    ret = 0
+    for filename in args.filenames:
+        try:
+            load_manifest(filename)
+        except InvalidManifestError as e:
+            print(e)
+            ret = 1
+    return ret
+
+
+LOCAL = 'local'
+META = 'meta'
+
+
+class MigrateShaToRev:
+    key = 'rev'
+
+    @staticmethod
+    def _cond(key: str) -> cfgv.Conditional:
+        return cfgv.Conditional(
+            key, cfgv.check_string,
+            condition_key='repo',
+            condition_value=cfgv.NotIn(LOCAL, META),
+            ensure_absent=True,
+        )
+
+    def check(self, dct: Dict[str, Any]) -> None:
+        if dct.get('repo') in {LOCAL, META}:
+            self._cond('rev').check(dct)
+            self._cond('sha').check(dct)
+        elif 'sha' in dct and 'rev' in dct:
+            raise cfgv.ValidationError('Cannot specify both sha and rev')
+        elif 'sha' in dct:
+            self._cond('sha').check(dct)
+        else:
+            self._cond('rev').check(dct)
+
+    def apply_default(self, dct: Dict[str, Any]) -> None:
+        if 'sha' in dct:
+            dct['rev'] = dct.pop('sha')
+
+    remove_default = cfgv.Required.remove_default
+
+
+def _entry(modname: str) -> str:
+    """the hook `entry` is passed through `shlex.split()` by the command
+    runner, so to prevent issues with spaces and backslashes (on Windows)
+    it must be quoted here.
+    """
+    return f'{shlex.quote(sys.executable)} -m pre_commit.meta_hooks.{modname}'
+
+
+def warn_unknown_keys_root(
+        extra: Sequence[str],
+        orig_keys: Sequence[str],
+        dct: Dict[str, str],
+) -> None:
+    logger.warning(f'Unexpected key(s) present at root: {", ".join(extra)}')
+
+
+def warn_unknown_keys_repo(
+        extra: Sequence[str],
+        orig_keys: Sequence[str],
+        dct: Dict[str, str],
+) -> None:
+    logger.warning(
+        f'Unexpected key(s) present on {dct["repo"]}: {", ".join(extra)}',
+    )
+
+
+_meta = (
+    (
+        'check-hooks-apply', (
+            ('name', 'Check hooks apply to the repository'),
+            ('files', C.CONFIG_FILE),
+            ('entry', _entry('check_hooks_apply')),
+        ),
+    ),
+    (
+        'check-useless-excludes', (
+            ('name', 'Check for useless excludes'),
+            ('files', C.CONFIG_FILE),
+            ('entry', _entry('check_useless_excludes')),
+        ),
+    ),
+    (
+        'identity', (
+            ('name', 'identity'),
+            ('verbose', True),
+            ('entry', _entry('identity')),
+        ),
+    ),
+)
+
+META_HOOK_DICT = cfgv.Map(
+    'Hook', 'id',
+    cfgv.Required('id', cfgv.check_string),
+    cfgv.Required('id', cfgv.check_one_of(tuple(k for k, _ in _meta))),
+    # language must be system
+    cfgv.Optional('language', cfgv.check_one_of({'system'}), 'system'),
+    *(
+        # default to the hook definition for the meta hooks
+        cfgv.ConditionalOptional(key, cfgv.check_any, value, 'id', hook_id)
+        for hook_id, values in _meta
+        for key, value in values
+    ),
+    *(
+        # default to the "manifest" parsing
+        cfgv.OptionalNoDefault(item.key, item.check_fn)
+        # these will always be defaulted above
+        if item.key in {'name', 'language', 'entry'} else
+        item
+        for item in MANIFEST_HOOK_DICT.items
+    ),
+)
+CONFIG_HOOK_DICT = cfgv.Map(
+    'Hook', 'id',
+
+    cfgv.Required('id', cfgv.check_string),
+
+    # All keys in manifest hook dict are valid in a config hook dict, but
+    # are optional.
+    # No defaults are provided here as the config is merged on top of the
+    # manifest.
+    *(
+        cfgv.OptionalNoDefault(item.key, item.check_fn)
+        for item in MANIFEST_HOOK_DICT.items
+        if item.key != 'id'
+    ),
+)
+CONFIG_REPO_DICT = cfgv.Map(
+    'Repository', 'repo',
+
+    cfgv.Required('repo', cfgv.check_string),
+
+    cfgv.ConditionalRecurse(
+        'hooks', cfgv.Array(CONFIG_HOOK_DICT),
+        'repo', cfgv.NotIn(LOCAL, META),
+    ),
+    cfgv.ConditionalRecurse(
+        'hooks', cfgv.Array(MANIFEST_HOOK_DICT),
+        'repo', LOCAL,
+    ),
+    cfgv.ConditionalRecurse(
+        'hooks', cfgv.Array(META_HOOK_DICT),
+        'repo', META,
+    ),
+
+    MigrateShaToRev(),
+    cfgv.WarnAdditionalKeys(('repo', 'rev', 'hooks'), warn_unknown_keys_repo),
+)
+DEFAULT_LANGUAGE_VERSION = cfgv.Map(
+    'DefaultLanguageVersion', None,
+    cfgv.NoAdditionalKeys(all_languages),
+    *(cfgv.Optional(x, cfgv.check_string, C.DEFAULT) for x in all_languages),
+)
+CONFIG_SCHEMA = cfgv.Map(
+    'Config', None,
+
+    cfgv.RequiredRecurse('repos', cfgv.Array(CONFIG_REPO_DICT)),
+    cfgv.OptionalRecurse(
+        'default_language_version', DEFAULT_LANGUAGE_VERSION, {},
+    ),
+    cfgv.Optional(
+        'default_stages',
+        cfgv.check_array(cfgv.check_one_of(C.STAGES)),
+        C.STAGES,
+    ),
+    cfgv.Optional('files', check_string_regex, ''),
+    cfgv.Optional('exclude', check_string_regex, '^$'),
+    cfgv.Optional('fail_fast', cfgv.check_bool, False),
+    cfgv.Optional(
+        'minimum_pre_commit_version',
+        cfgv.check_and(cfgv.check_string, check_min_version),
+        '0',
+    ),
+    cfgv.WarnAdditionalKeys(
+        (
+            'repos',
+            'default_language_version',
+            'default_stages',
+            'files',
+            'exclude',
+            'fail_fast',
+            'minimum_pre_commit_version',
+        ),
+        warn_unknown_keys_root,
+    ),
+)
+
+
+class InvalidConfigError(FatalError):
+    pass
+
+
+def ordered_load_normalize_legacy_config(contents: str) -> Dict[str, Any]:
+    data = yaml_load(contents)
+    if isinstance(data, list):
+        # TODO: Once happy, issue a deprecation warning and instructions
+        return {'repos': data}
+    else:
+        return data
+
+
+load_config = functools.partial(
+    cfgv.load_from_filename,
+    schema=CONFIG_SCHEMA,
+    load_strategy=ordered_load_normalize_legacy_config,
+    exc_tp=InvalidConfigError,
+)
+
+
+def validate_config_main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = _make_argparser('Config filenames.')
+    args = parser.parse_args(argv)
+    ret = 0
+    for filename in args.filenames:
+        try:
+            load_config(filename)
+        except InvalidConfigError as e:
+            print(e)
+            ret = 1
+    return ret
diff --git a/pre_commit/color.py b/pre_commit/color.py
new file mode 100644
index 0000000..5fa7042
--- /dev/null
+++ b/pre_commit/color.py
@@ -0,0 +1,97 @@
+import os
+import sys
+
+if sys.platform == 'win32':  # pragma: no cover (windows)
+    def _enable() -> None:
+        from ctypes import POINTER
+        from ctypes import windll
+        from ctypes import WinError
+        from ctypes import WINFUNCTYPE
+        from ctypes.wintypes import BOOL
+        from ctypes.wintypes import DWORD
+        from ctypes.wintypes import HANDLE
+
+        STD_OUTPUT_HANDLE = -11
+        ENABLE_VIRTUAL_TERMINAL_PROCESSING = 4
+
+        def bool_errcheck(result, func, args):
+            if not result:
+                raise WinError()
+            return args
+
+        GetStdHandle = WINFUNCTYPE(HANDLE, DWORD)(
+            ('GetStdHandle', windll.kernel32), ((1, 'nStdHandle'),),
+        )
+
+        GetConsoleMode = WINFUNCTYPE(BOOL, HANDLE, POINTER(DWORD))(
+            ('GetConsoleMode', windll.kernel32),
+            ((1, 'hConsoleHandle'), (2, 'lpMode')),
+        )
+        GetConsoleMode.errcheck = bool_errcheck
+
+        SetConsoleMode = WINFUNCTYPE(BOOL, HANDLE, DWORD)(
+            ('SetConsoleMode', windll.kernel32),
+            ((1, 'hConsoleHandle'), (1, 'dwMode')),
+        )
+        SetConsoleMode.errcheck = bool_errcheck
+
+        # As of Windows 10, the Windows console supports (some) ANSI escape
+        # sequences, but it needs to be enabled using `SetConsoleMode` first.
+        #
+        # More info on the escape sequences supported:
+        # https://msdn.microsoft.com/en-us/library/windows/desktop/mt638032(v=vs.85).aspx
+        stdout = GetStdHandle(STD_OUTPUT_HANDLE)
+        flags = GetConsoleMode(stdout)
+        SetConsoleMode(stdout, flags | ENABLE_VIRTUAL_TERMINAL_PROCESSING)
+
+    try:
+        _enable()
+    except OSError:
+        terminal_supports_color = False
+    else:
+        terminal_supports_color = True
+else:  # pragma: win32 no cover
+    terminal_supports_color = True
+
+RED = '\033[41m'
+GREEN = '\033[42m'
+YELLOW = '\033[43;30m'
+TURQUOISE = '\033[46;30m'
+SUBTLE = '\033[2m'
+NORMAL = '\033[m'
+
+
+def format_color(text: str, color: str, use_color_setting: bool) -> str:
+    """Format text with color.
+
+    Args:
+        text - Text to be formatted with color if `use_color`
+        color - The color start string
+        use_color_setting - Whether or not to color
+    """
+    if use_color_setting:
+        return f'{color}{text}{NORMAL}'
+    else:
+        return text
+
+
+COLOR_CHOICES = ('auto', 'always', 'never')
+
+
+def use_color(setting: str) -> bool:
+    """Choose whether to use color based on the command argument.
+
+    Args:
+        setting - Either `auto`, `always`, or `never`
+    """
+    if setting not in COLOR_CHOICES:
+        raise ValueError(setting)
+
+    return (
+        setting == 'always' or (
+            setting == 'auto' and
+            sys.stdout.isatty() and
+            terminal_supports_color and
+            os.getenv('TERM') != 'dumb'
+        )
+    )
diff --git a/pre_commit/commands/__init__.py b/pre_commit/commands/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/pre_commit/commands/__init__.py
diff --git a/pre_commit/commands/autoupdate.py b/pre_commit/commands/autoupdate.py
new file mode 100644
index 0000000..5a9a988
--- /dev/null
+++ b/pre_commit/commands/autoupdate.py
@@ -0,0 +1,182 @@
+import os.path
+import re
+from typing import Any
+from typing import Dict
+from typing import List
+from typing import NamedTuple
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit import git
+from pre_commit import output
+from pre_commit.clientlib import InvalidManifestError
+from pre_commit.clientlib import load_config
+from pre_commit.clientlib import load_manifest
+from pre_commit.clientlib import LOCAL
+from pre_commit.clientlib import META
+from pre_commit.commands.migrate_config import migrate_config
+from pre_commit.store import Store
+from pre_commit.util import CalledProcessError
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+from pre_commit.util import tmpdir
+from pre_commit.util import yaml_dump
+from pre_commit.util import yaml_load
+
+
+class RevInfo(NamedTuple):
+    repo: str
+    rev: str
+    frozen: Optional[str]
+
+    @classmethod
+    def from_config(cls, config: Dict[str, Any]) -> 'RevInfo':
+        return cls(config['repo'], config['rev'], None)
+
+    def update(self, tags_only: bool, freeze: bool) -> 'RevInfo':
+        if tags_only:
+            tag_cmd = ('git', 'describe', 'FETCH_HEAD', '--tags', '--abbrev=0')
+        else:
+            tag_cmd = ('git', 'describe', 'FETCH_HEAD', '--tags', '--exact')
+
+        with tmpdir() as tmp:
+            git.init_repo(tmp, self.repo)
+            cmd_output_b('git', 'fetch', 'origin', 'HEAD', '--tags', cwd=tmp)
+
+            try:
+                rev = cmd_output(*tag_cmd, cwd=tmp)[1].strip()
+            except CalledProcessError:
+                cmd = ('git', 'rev-parse', 'FETCH_HEAD')
+                rev = cmd_output(*cmd, cwd=tmp)[1].strip()
+
+            frozen = None
+            if freeze:
+                exact = cmd_output('git', 'rev-parse', rev, cwd=tmp)[1].strip()
+                if exact != rev:
+                    rev, frozen = exact, rev
+        return self._replace(rev=rev, frozen=frozen)
+
+
+class RepositoryCannotBeUpdatedError(RuntimeError):
+    pass
+
+
+def _check_hooks_still_exist_at_rev(
+        repo_config: Dict[str, Any],
+        info: RevInfo,
+        store: Store,
+) -> None:
+    try:
+        path = store.clone(repo_config['repo'], info.rev)
+        manifest = load_manifest(os.path.join(path, C.MANIFEST_FILE))
+    except InvalidManifestError as e:
+        raise RepositoryCannotBeUpdatedError(str(e))
+
+    # See if any of our hooks were deleted with the new commits
+    hooks = {hook['id'] for hook in repo_config['hooks']}
+    hooks_missing = hooks - {hook['id'] for hook in manifest}
+    if hooks_missing:
+        raise RepositoryCannotBeUpdatedError(
+            f'Cannot update because the tip of HEAD is missing these hooks:\n'
+            f'{", ".join(sorted(hooks_missing))}',
+        )
+
+
+REV_LINE_RE = re.compile(r'^(\s+)rev:(\s*)([^\s#]+)(.*)(\r?\n)$', re.DOTALL)
+
+
+def _original_lines(
+        path: str,
+        rev_infos: List[Optional[RevInfo]],
+        retry: bool = False,
+) -> Tuple[List[str], List[int]]:
+    """detect `rev:` lines or reformat the file"""
+    with open(path) as f:
+        original = f.read()
+
+    lines = original.splitlines(True)
+    idxs = [i for i, line in enumerate(lines) if REV_LINE_RE.match(line)]
+    if len(idxs) == len(rev_infos):
+        return lines, idxs
+    elif retry:
+        raise AssertionError('could not find rev lines')
+    else:
+        with open(path, 'w') as f:
+            f.write(yaml_dump(yaml_load(original)))
+        return _original_lines(path, rev_infos, retry=True)
+
+
+def _write_new_config(path: str, rev_infos: List[Optional[RevInfo]]) -> None:
+    lines, idxs = _original_lines(path, rev_infos)
+
+    for idx, rev_info in zip(idxs, rev_infos):
+        if rev_info is None:
+            continue
+        match = REV_LINE_RE.match(lines[idx])
+        assert match is not None
+        new_rev_s = yaml_dump({'rev': rev_info.rev})
+        new_rev = new_rev_s.split(':', 1)[1].strip()
+        if rev_info.frozen is not None:
+            comment = f'  # frozen: {rev_info.frozen}'
+        elif match[4].strip().startswith('# frozen:'):
+            comment = ''
+        else:
+            comment = match[4]
+        lines[idx] = f'{match[1]}rev:{match[2]}{new_rev}{comment}{match[5]}'
+
+    with open(path, 'w') as f:
+        f.write(''.join(lines))
+
+
+def autoupdate(
+        config_file: str,
+        store: Store,
+        tags_only: bool,
+        freeze: bool,
+        repos: Sequence[str] = (),
+) -> int:
+    """Auto-update the pre-commit config to the latest versions of repos."""
+    migrate_config(config_file, quiet=True)
+    retv = 0
+    rev_infos: List[Optional[RevInfo]] = []
+    changed = False
+
+    config = load_config(config_file)
+    for repo_config in config['repos']:
+        if repo_config['repo'] in {LOCAL, META}:
+            continue
+
+        info = RevInfo.from_config(repo_config)
+        if repos and info.repo not in repos:
+            rev_infos.append(None)
+            continue
+
+        output.write(f'Updating {info.repo} ... ')
+        new_info = info.update(tags_only=tags_only, freeze=freeze)
+        try:
+            _check_hooks_still_exist_at_rev(repo_config, new_info, store)
+        except RepositoryCannotBeUpdatedError as error:
+            output.write_line(error.args[0])
+            rev_infos.append(None)
+            retv = 1
+            continue
+
+        if new_info.rev != info.rev:
+            changed = True
+            if new_info.frozen:
+                updated_to = f'{new_info.frozen} (frozen)'
+            else:
+                updated_to = new_info.rev
+            msg = f'updating {info.rev} -> {updated_to}.'
+            output.write_line(msg)
+            rev_infos.append(new_info)
+        else:
+            output.write_line('already up to date.')
+            rev_infos.append(None)
+
+    if changed:
+        _write_new_config(config_file, rev_infos)
+
+    return retv
diff --git a/pre_commit/commands/clean.py b/pre_commit/commands/clean.py
new file mode 100644
index 0000000..2be6c16
--- /dev/null
+++ b/pre_commit/commands/clean.py
@@ -0,0 +1,14 @@
+import os.path
+
+from pre_commit import output
+from pre_commit.store import Store
+from pre_commit.util import rmtree
+
+
+def clean(store: Store) -> int:
+    legacy_path = os.path.expanduser('~/.pre-commit')
+    for directory in (store.directory, legacy_path):
+        if os.path.exists(directory):
+            rmtree(directory)
+            output.write_line(f'Cleaned {directory}.')
+    return 0
diff --git a/pre_commit/commands/gc.py b/pre_commit/commands/gc.py
new file mode 100644
index 0000000..7f6d311
--- /dev/null
+++ b/pre_commit/commands/gc.py
@@ -0,0 +1,90 @@
+import os.path
+from typing import Any
+from typing import Dict
+from typing import Set
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit import output
+from pre_commit.clientlib import InvalidConfigError
+from pre_commit.clientlib import InvalidManifestError
+from pre_commit.clientlib import load_config
+from pre_commit.clientlib import load_manifest
+from pre_commit.clientlib import LOCAL
+from pre_commit.clientlib import META
+from pre_commit.store import Store
+
+
+def _mark_used_repos(
+        store: Store,
+        all_repos: Dict[Tuple[str, str], str],
+        unused_repos: Set[Tuple[str, str]],
+        repo: Dict[str, Any],
+) -> None:
+    if repo['repo'] == META:
+        return
+    elif repo['repo'] == LOCAL:
+        for hook in repo['hooks']:
+            deps = hook.get('additional_dependencies')
+            unused_repos.discard((
+                store.db_repo_name(repo['repo'], deps), C.LOCAL_REPO_VERSION,
+            ))
+    else:
+        key = (repo['repo'], repo['rev'])
+        path = all_repos.get(key)
+        # can't inspect manifest if it isn't cloned
+        if path is None:
+            return
+
+        try:
+            manifest = load_manifest(os.path.join(path, C.MANIFEST_FILE))
+        except InvalidManifestError:
+            return
+        else:
+            unused_repos.discard(key)
+            by_id = {hook['id']: hook for hook in manifest}
+
+        for hook in repo['hooks']:
+            if hook['id'] not in by_id:
+                continue
+
+            deps = hook.get(
+                'additional_dependencies',
+                by_id[hook['id']]['additional_dependencies'],
+            )
+            unused_repos.discard((
+                store.db_repo_name(repo['repo'], deps), repo['rev'],
+            ))
+
+
+def _gc_repos(store: Store) -> int:
+    configs = store.select_all_configs()
+    repos = store.select_all_repos()
+
+    # delete config paths which do not exist
+    dead_configs = [p for p in configs if not os.path.exists(p)]
+    live_configs = [p for p in configs if os.path.exists(p)]
+
+    all_repos = {(repo, ref): path for repo, ref, path in repos}
+    unused_repos = set(all_repos)
+    for config_path in live_configs:
+        try:
+            config = load_config(config_path)
+        except InvalidConfigError:
+            dead_configs.append(config_path)
+            continue
+        else:
+            for repo in config['repos']:
+                _mark_used_repos(store, all_repos, unused_repos, repo)
+
+    store.delete_configs(dead_configs)
+    for db_repo_name, ref in unused_repos:
+        store.delete_repo(db_repo_name, ref, all_repos[(db_repo_name, ref)])
+    return len(unused_repos)
+
+
+def gc(store: Store) -> int:
+    with store.exclusive_lock():
+        repos_removed = _gc_repos(store)
+    output.write_line(f'{repos_removed} repo(s) removed.')
+    return 0
diff --git a/pre_commit/commands/hook_impl.py b/pre_commit/commands/hook_impl.py
new file mode 100644
index 0000000..5ff4555
--- /dev/null
+++ b/pre_commit/commands/hook_impl.py
@@ -0,0 +1,187 @@
+import argparse
+import os.path
+import subprocess
+import sys
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.commands.run import run
+from pre_commit.envcontext import envcontext
+from pre_commit.parse_shebang import normalize_cmd
+from pre_commit.store import Store
+
+Z40 = '0' * 40
+
+
+def _run_legacy(
+        hook_type: str,
+        hook_dir: str,
+        args: Sequence[str],
+) -> Tuple[int, bytes]:
+    if os.environ.get('PRE_COMMIT_RUNNING_LEGACY'):
+        raise SystemExit(
+            f"bug: pre-commit's script is installed in migration mode\n"
+            f'run `pre-commit install -f --hook-type {hook_type}` to fix '
+            f'this\n\n'
+            f'Please report this bug at '
+            f'https://github.com/pre-commit/pre-commit/issues',
+        )
+
+    if hook_type == 'pre-push':
+        stdin = sys.stdin.buffer.read()
+    else:
+        stdin = b''
+
+    # not running in legacy mode
+    legacy_hook = os.path.join(hook_dir, f'{hook_type}.legacy')
+    if not os.access(legacy_hook, os.X_OK):
+        return 0, stdin
+
+    with envcontext((('PRE_COMMIT_RUNNING_LEGACY', '1'),)):
+        cmd = normalize_cmd((legacy_hook, *args))
+        return subprocess.run(cmd, input=stdin).returncode, stdin
+
+
+def _validate_config(
+        retv: int,
+        config: str,
+        skip_on_missing_config: bool,
+) -> None:
+    if not os.path.isfile(config):
+        if skip_on_missing_config or os.getenv('PRE_COMMIT_ALLOW_NO_CONFIG'):
+            print(f'`{config}` config file not found. Skipping `pre-commit`.')
+            raise SystemExit(retv)
+        else:
+            print(
+                f'No {config} file was found\n'
+                f'- To temporarily silence this, run '
+                f'`PRE_COMMIT_ALLOW_NO_CONFIG=1 git ...`\n'
+                f'- To permanently silence this, install pre-commit with the '
+                f'--allow-missing-config option\n'
+                f'- To uninstall pre-commit run `pre-commit uninstall`',
+            )
+            raise SystemExit(1)
+
+
+def _ns(
+        hook_type: str,
+        color: bool,
+        *,
+        all_files: bool = False,
+        from_ref: Optional[str] = None,
+        to_ref: Optional[str] = None,
+        remote_name: Optional[str] = None,
+        remote_url: Optional[str] = None,
+        commit_msg_filename: Optional[str] = None,
+        checkout_type: Optional[str] = None,
+) -> argparse.Namespace:
+    return argparse.Namespace(
+        color=color,
+        hook_stage=hook_type.replace('pre-', ''),
+        from_ref=from_ref,
+        to_ref=to_ref,
+        remote_name=remote_name,
+        remote_url=remote_url,
+        commit_msg_filename=commit_msg_filename,
+        all_files=all_files,
+        checkout_type=checkout_type,
+        files=(),
+        hook=None,
+        verbose=False,
+        show_diff_on_failure=False,
+    )
+
+
+def _rev_exists(rev: str) -> bool:
+    return not subprocess.call(('git', 'rev-list', '--quiet', rev))
+
+
+def _pre_push_ns(
+        color: bool,
+        args: Sequence[str],
+        stdin: bytes,
+) -> Optional[argparse.Namespace]:
+    remote_name = args[0]
+    remote_url = args[1]
+
+    for line in stdin.decode().splitlines():
+        _, local_sha, _, remote_sha = line.split()
+        if local_sha == Z40:
+            continue
+        elif remote_sha != Z40 and _rev_exists(remote_sha):
+            return _ns(
+                'pre-push', color,
+                from_ref=remote_sha, to_ref=local_sha,
+                remote_name=remote_name, remote_url=remote_url,
+            )
+        else:
+            # ancestors not found in remote
+            ancestors = subprocess.check_output((
+                'git', 'rev-list', local_sha, '--topo-order', '--reverse',
+                '--not', f'--remotes={remote_name}',
+            )).decode().strip()
+            if not ancestors:
+                continue
+            else:
+                first_ancestor = ancestors.splitlines()[0]
+                cmd = ('git', 'rev-list', '--max-parents=0', local_sha)
+                roots = set(subprocess.check_output(cmd).decode().splitlines())
+                if first_ancestor in roots:
+                    # pushing the whole tree including root commit
+                    return _ns(
+                        'pre-push', color,
+                        all_files=True,
+                        remote_name=remote_name, remote_url=remote_url,
+                    )
+                else:
+                    rev_cmd = ('git', 'rev-parse', f'{first_ancestor}^')
+                    source = subprocess.check_output(rev_cmd).decode().strip()
+                    return _ns(
+                        'pre-push', color,
+                        from_ref=source, to_ref=local_sha,
+                        remote_name=remote_name, remote_url=remote_url,
+                    )
+
+    # nothing to push
+    return None
+
+
+def _run_ns(
+        hook_type: str,
+        color: bool,
+        args: Sequence[str],
+        stdin: bytes,
+) -> Optional[argparse.Namespace]:
+    if hook_type == 'pre-push':
+        return _pre_push_ns(color, args, stdin)
+    elif hook_type in {'prepare-commit-msg', 'commit-msg'}:
+        return _ns(hook_type, color, commit_msg_filename=args[0])
+    elif hook_type in {'pre-merge-commit', 'pre-commit'}:
+        return _ns(hook_type, color)
+    elif hook_type == 'post-checkout':
+        return _ns(
+            hook_type, color,
+            from_ref=args[0], to_ref=args[1], checkout_type=args[2],
+        )
+    else:
+        raise AssertionError(f'unexpected hook type: {hook_type}')
+
+
+def hook_impl(
+        store: Store,
+        *,
+        config: str,
+        color: bool,
+        hook_type: str,
+        hook_dir: str,
+        skip_on_missing_config: bool,
+        args: Sequence[str],
+) -> int:
+    retv, stdin = _run_legacy(hook_type, hook_dir, args)
+    _validate_config(retv, config, skip_on_missing_config)
+    ns = _run_ns(hook_type, color, args, stdin)
+    if ns is None:
+        return retv
+    else:
+        return retv | run(config, store, ns)
diff --git a/pre_commit/commands/init_templatedir.py b/pre_commit/commands/init_templatedir.py
new file mode 100644
index 0000000..f676fb1
--- /dev/null
+++ b/pre_commit/commands/init_templatedir.py
@@ -0,0 +1,33 @@
+import logging
+import os.path
+from typing import Sequence
+
+from pre_commit.commands.install_uninstall import install
+from pre_commit.store import Store
+from pre_commit.util import CalledProcessError
+from pre_commit.util import cmd_output
+
+logger = logging.getLogger('pre_commit')
+
+
+def init_templatedir(
+        config_file: str,
+        store: Store,
+        directory: str,
+        hook_types: Sequence[str],
+) -> int:
+    install(
+        config_file, store, hook_types=hook_types,
+        overwrite=True, skip_on_missing_config=True, git_dir=directory,
+    )
+    try:
+        _, out, _ = cmd_output('git', 'config', 'init.templateDir')
+    except CalledProcessError:
+        configured_path = None
+    else:
+        configured_path = os.path.realpath(os.path.expanduser(out.strip()))
+    dest = os.path.realpath(directory)
+    if configured_path != dest:
+        logger.warning('`init.templateDir` not set to the target directory')
+        logger.warning(f'maybe `git config --global init.templateDir {dest}`?')
+    return 0
diff --git a/pre_commit/commands/install_uninstall.py b/pre_commit/commands/install_uninstall.py
new file mode 100644
index 0000000..c8b7633
--- /dev/null
+++ b/pre_commit/commands/install_uninstall.py
@@ -0,0 +1,175 @@
+import itertools
+import logging
+import os.path
+import shutil
+import sys
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit import git
+from pre_commit import output
+from pre_commit.clientlib import load_config
+from pre_commit.repository import all_hooks
+from pre_commit.repository import install_hook_envs
+from pre_commit.store import Store
+from pre_commit.util import make_executable
+from pre_commit.util import resource_text
+
+
+logger = logging.getLogger(__name__)
+
+# This is used to identify the hook file we install
+PRIOR_HASHES = (
+    '4d9958c90bc262f47553e2c073f14cfe',
+    'd8ee923c46731b42cd95cc869add4062',
+    '49fd668cb42069aa1b6048464be5d395',
+    '79f09a650522a87b0da915d0d983b2de',
+    'e358c9dae00eac5d06b38dfdb1e33a8c',
+)
+CURRENT_HASH = '138fd403232d2ddd5efb44317e38bf03'
+TEMPLATE_START = '# start templated\n'
+TEMPLATE_END = '# end templated\n'
+# Homebrew/homebrew-core#35825: be more timid about appropriate `PATH`
+# #1312 os.defpath is too restrictive on BSD
+POSIX_SEARCH_PATH = ('/usr/local/bin', '/usr/bin', '/bin')
+SYS_EXE = os.path.basename(os.path.realpath(sys.executable))
+
+
+def _hook_paths(
+        hook_type: str,
+        git_dir: Optional[str] = None,
+) -> Tuple[str, str]:
+    git_dir = git_dir if git_dir is not None else git.get_git_dir()
+    pth = os.path.join(git_dir, 'hooks', hook_type)
+    return pth, f'{pth}.legacy'
+
+
+def is_our_script(filename: str) -> bool:
+    if not os.path.exists(filename):  # pragma: win32 no cover (symlink)
+        return False
+    with open(filename) as f:
+        contents = f.read()
+    return any(h in contents for h in (CURRENT_HASH,) + PRIOR_HASHES)
+
+
+def shebang() -> str:
+    if sys.platform == 'win32':
+        py = SYS_EXE
+    else:
+        exe_choices = [
+            f'python{sys.version_info[0]}.{sys.version_info[1]}',
+            f'python{sys.version_info[0]}',
+        ]
+        # avoid searching for bare `python` as it's likely to be python 2
+        if SYS_EXE != 'python':
+            exe_choices.append(SYS_EXE)
+        for path, exe in itertools.product(POSIX_SEARCH_PATH, exe_choices):
+            if os.access(os.path.join(path, exe), os.X_OK):
+                py = exe
+                break
+        else:
+            py = SYS_EXE
+    return f'#!/usr/bin/env {py}'
+
+
+def _install_hook_script(
+        config_file: str,
+        hook_type: str,
+        overwrite: bool = False,
+        skip_on_missing_config: bool = False,
+        git_dir: Optional[str] = None,
+) -> None:
+    hook_path, legacy_path = _hook_paths(hook_type, git_dir=git_dir)
+
+    os.makedirs(os.path.dirname(hook_path), exist_ok=True)
+
+    # If we have an existing hook, move it to pre-commit.legacy
+    if os.path.lexists(hook_path) and not is_our_script(hook_path):
+        shutil.move(hook_path, legacy_path)
+
+    # If we specify overwrite, we simply delete the legacy file
+    if overwrite and os.path.exists(legacy_path):
+        os.remove(legacy_path)
+    elif os.path.exists(legacy_path):
+        output.write_line(
+            f'Running in migration mode with existing hooks at {legacy_path}\n'
+            f'Use -f to use only pre-commit.',
+        )
+
+    args = ['hook-impl', f'--config={config_file}', f'--hook-type={hook_type}']
+    if skip_on_missing_config:
+        args.append('--skip-on-missing-config')
+    params = {'INSTALL_PYTHON': sys.executable, 'ARGS': args}
+
+    with open(hook_path, 'w') as hook_file:
+        contents = resource_text('hook-tmpl')
+        before, rest = contents.split(TEMPLATE_START)
+        to_template, after = rest.split(TEMPLATE_END)
+
+        before = before.replace('#!/usr/bin/env python3', shebang())
+
+        hook_file.write(before + TEMPLATE_START)
+        for line in to_template.splitlines():
+            var = line.split()[0]
+            hook_file.write(f'{var} = {params[var]!r}\n')
+        hook_file.write(TEMPLATE_END + after)
+    make_executable(hook_path)
+
+    output.write_line(f'pre-commit installed at {hook_path}')
+
+
+def install(
+        config_file: str,
+        store: Store,
+        hook_types: Sequence[str],
+        overwrite: bool = False,
+        hooks: bool = False,
+        skip_on_missing_config: bool = False,
+        git_dir: Optional[str] = None,
+) -> int:
+    if git_dir is None and git.has_core_hookpaths_set():
+        logger.error(
+            'Cowardly refusing to install hooks with `core.hooksPath` set.\n'
+            'hint: `git config --unset-all core.hooksPath`',
+        )
+        return 1
+
+    for hook_type in hook_types:
+        _install_hook_script(
+            config_file, hook_type,
+            overwrite=overwrite,
+            skip_on_missing_config=skip_on_missing_config,
+            git_dir=git_dir,
+        )
+
+    if hooks:
+        install_hooks(config_file, store)
+
+    return 0
+
+
+def install_hooks(config_file: str, store: Store) -> int:
+    install_hook_envs(all_hooks(load_config(config_file), store), store)
+    return 0
+
+
+def _uninstall_hook_script(hook_type: str) -> None:
+    hook_path, legacy_path = _hook_paths(hook_type)
+
+    # If our file doesn't exist or it isn't ours, gtfo.
+    if not os.path.exists(hook_path) or not is_our_script(hook_path):
+        return
+
+    os.remove(hook_path)
+    output.write_line(f'{hook_type} uninstalled')
+
+    if os.path.exists(legacy_path):
+        os.rename(legacy_path, hook_path)
+        output.write_line(f'Restored previous hooks to {hook_path}')
+
+
+def uninstall(hook_types: Sequence[str]) -> int:
+    for hook_type in hook_types:
+        _uninstall_hook_script(hook_type)
+    return 0
diff --git a/pre_commit/commands/migrate_config.py b/pre_commit/commands/migrate_config.py
new file mode 100644
index 0000000..d83b8e9
--- /dev/null
+++ b/pre_commit/commands/migrate_config.py
@@ -0,0 +1,59 @@
+import re
+
+import yaml
+
+from pre_commit.util import yaml_load
+
+
+def _indent(s: str) -> str:
+    lines = s.splitlines(True)
+    return ''.join(' ' * 4 + line if line.strip() else line for line in lines)
+
+
+def _is_header_line(line: str) -> bool:
+    return line.startswith(('#', '---')) or not line.strip()
+
+
+def _migrate_map(contents: str) -> str:
+    # Find the first non-header line
+    lines = contents.splitlines(True)
+    i = 0
+    # Only loop on non empty configuration file
+    while i < len(lines) and _is_header_line(lines[i]):
+        i += 1
+
+    header = ''.join(lines[:i])
+    rest = ''.join(lines[i:])
+
+    if isinstance(yaml_load(contents), list):
+        # If they are using the "default" flow style of yaml, this operation
+        # will yield a valid configuration
+        try:
+            trial_contents = f'{header}repos:\n{rest}'
+            yaml_load(trial_contents)
+            contents = trial_contents
+        except yaml.YAMLError:
+            contents = f'{header}repos:\n{_indent(rest)}'
+
+    return contents
+
+
+def _migrate_sha_to_rev(contents: str) -> str:
+    return re.sub(r'(\n\s+)sha:', r'\1rev:', contents)
+
+
+def migrate_config(config_file: str, quiet: bool = False) -> int:
+    with open(config_file) as f:
+        orig_contents = contents = f.read()
+
+    contents = _migrate_map(contents)
+    contents = _migrate_sha_to_rev(contents)
+
+    if contents != orig_contents:
+        with open(config_file, 'w') as f:
+            f.write(contents)
+
+        print('Configuration has been migrated.')
+    elif not quiet:
+        print('Configuration is already migrated.')
+    return 0
diff --git a/pre_commit/commands/run.py b/pre_commit/commands/run.py
new file mode 100644
index 0000000..2f74578
--- /dev/null
+++ b/pre_commit/commands/run.py
@@ -0,0 +1,360 @@
+import argparse
+import contextlib
+import functools
+import logging
+import os
+import re
+import subprocess
+import time
+from typing import Any
+from typing import Collection
+from typing import Dict
+from typing import List
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+
+from identify.identify import tags_from_path
+
+from pre_commit import color
+from pre_commit import git
+from pre_commit import output
+from pre_commit.clientlib import load_config
+from pre_commit.hook import Hook
+from pre_commit.languages.all import languages
+from pre_commit.repository import all_hooks
+from pre_commit.repository import install_hook_envs
+from pre_commit.staged_files_only import staged_files_only
+from pre_commit.store import Store
+from pre_commit.util import cmd_output_b
+from pre_commit.util import EnvironT
+
+
+logger = logging.getLogger('pre_commit')
+
+
+def _start_msg(*, start: str, cols: int, end_len: int) -> str:
+    dots = '.' * (cols - len(start) - end_len - 1)
+    return f'{start}{dots}'
+
+
+def _full_msg(
+        *,
+        start: str,
+        cols: int,
+        end_msg: str,
+        end_color: str,
+        use_color: bool,
+        postfix: str = '',
+) -> str:
+    dots = '.' * (cols - len(start) - len(postfix) - len(end_msg) - 1)
+    end = color.format_color(end_msg, end_color, use_color)
+    return f'{start}{dots}{postfix}{end}\n'
+
+
+def filter_by_include_exclude(
+        names: Collection[str],
+        include: str,
+        exclude: str,
+) -> List[str]:
+    include_re, exclude_re = re.compile(include), re.compile(exclude)
+    return [
+        filename for filename in names
+        if include_re.search(filename)
+        if not exclude_re.search(filename)
+    ]
+
+
+class Classifier:
+    def __init__(self, filenames: Sequence[str]) -> None:
+        # on windows we normalize all filenames to use forward slashes
+        # this makes it easier to filter using the `files:` regex
+        # this also makes improperly quoted shell-based hooks work better
+        # see #1173
+        if os.altsep == '/' and os.sep == '\\':
+            filenames = [f.replace(os.sep, os.altsep) for f in filenames]
+        self.filenames = [f for f in filenames if os.path.lexists(f)]
+
+    @functools.lru_cache(maxsize=None)
+    def _types_for_file(self, filename: str) -> Set[str]:
+        return tags_from_path(filename)
+
+    def by_types(
+            self,
+            names: Sequence[str],
+            types: Collection[str],
+            exclude_types: Collection[str],
+    ) -> List[str]:
+        types, exclude_types = frozenset(types), frozenset(exclude_types)
+        ret = []
+        for filename in names:
+            tags = self._types_for_file(filename)
+            if tags >= types and not tags & exclude_types:
+                ret.append(filename)
+        return ret
+
+    def filenames_for_hook(self, hook: Hook) -> Tuple[str, ...]:
+        names = self.filenames
+        names = filter_by_include_exclude(names, hook.files, hook.exclude)
+        names = self.by_types(names, hook.types, hook.exclude_types)
+        return tuple(names)
+
+
+def _get_skips(environ: EnvironT) -> Set[str]:
+    skips = environ.get('SKIP', '')
+    return {skip.strip() for skip in skips.split(',') if skip.strip()}
+
+
+SKIPPED = 'Skipped'
+NO_FILES = '(no files to check)'
+
+
+def _subtle_line(s: str, use_color: bool) -> None:
+    output.write_line(color.format_color(s, color.SUBTLE, use_color))
+
+
+def _run_single_hook(
+        classifier: Classifier,
+        hook: Hook,
+        skips: Set[str],
+        cols: int,
+        verbose: bool,
+        use_color: bool,
+) -> bool:
+    filenames = classifier.filenames_for_hook(hook)
+
+    if hook.id in skips or hook.alias in skips:
+        output.write(
+            _full_msg(
+                start=hook.name,
+                end_msg=SKIPPED,
+                end_color=color.YELLOW,
+                use_color=use_color,
+                cols=cols,
+            ),
+        )
+        duration = None
+        retcode = 0
+        files_modified = False
+        out = b''
+    elif not filenames and not hook.always_run:
+        output.write(
+            _full_msg(
+                start=hook.name,
+                postfix=NO_FILES,
+                end_msg=SKIPPED,
+                end_color=color.TURQUOISE,
+                use_color=use_color,
+                cols=cols,
+            ),
+        )
+        duration = None
+        retcode = 0
+        files_modified = False
+        out = b''
+    else:
+        # print hook and dots first in case the hook takes a while to run
+        output.write(_start_msg(start=hook.name, end_len=6, cols=cols))
+
+        diff_cmd = ('git', 'diff', '--no-ext-diff')
+        diff_before = cmd_output_b(*diff_cmd, retcode=None)
+        if not hook.pass_filenames:
+            filenames = ()
+        time_before = time.time()
+        language = languages[hook.language]
+        retcode, out = language.run_hook(hook, filenames, use_color)
+        duration = round(time.time() - time_before, 2) or 0
+        diff_after = cmd_output_b(*diff_cmd, retcode=None)
+
+        # if the hook makes changes, fail the commit
+        files_modified = diff_before != diff_after
+
+        if retcode or files_modified:
+            print_color = color.RED
+            status = 'Failed'
+        else:
+            print_color = color.GREEN
+            status = 'Passed'
+
+        output.write_line(color.format_color(status, print_color, use_color))
+
+    if verbose or hook.verbose or retcode or files_modified:
+        _subtle_line(f'- hook id: {hook.id}', use_color)
+
+        if (verbose or hook.verbose) and duration is not None:
+            _subtle_line(f'- duration: {duration}s', use_color)
+
+        if retcode:
+            _subtle_line(f'- exit code: {retcode}', use_color)
+
+        # Print a message if failing due to file modifications
+        if files_modified:
+            _subtle_line('- files were modified by this hook', use_color)
+
+        if out.strip():
+            output.write_line()
+            output.write_line_b(out.strip(), logfile_name=hook.log_file)
+            output.write_line()
+
+    return files_modified or bool(retcode)
+
+
+def _compute_cols(hooks: Sequence[Hook]) -> int:
+    """Compute the number of columns to display hook messages.  The widest
+    that will be displayed is in the no files skipped case:
+
+        Hook name...(no files to check) Skipped
+    """
+    if hooks:
+        name_len = max(len(hook.name) for hook in hooks)
+    else:
+        name_len = 0
+
+    cols = name_len + 3 + len(NO_FILES) + 1 + len(SKIPPED)
+    return max(cols, 80)
+
+
+def _all_filenames(args: argparse.Namespace) -> Collection[str]:
+    if args.hook_stage == 'post-checkout':  # no files for post-checkout
+        return ()
+    elif args.hook_stage in {'prepare-commit-msg', 'commit-msg'}:
+        return (args.commit_msg_filename,)
+    elif args.from_ref and args.to_ref:
+        return git.get_changed_files(args.from_ref, args.to_ref)
+    elif args.files:
+        return args.files
+    elif args.all_files:
+        return git.get_all_files()
+    elif git.is_in_merge_conflict():
+        return git.get_conflicted_files()
+    else:
+        return git.get_staged_files()
+
+
+def _run_hooks(
+        config: Dict[str, Any],
+        hooks: Sequence[Hook],
+        args: argparse.Namespace,
+        environ: EnvironT,
+) -> int:
+    """Actually run the hooks."""
+    skips = _get_skips(environ)
+    cols = _compute_cols(hooks)
+    filenames = filter_by_include_exclude(
+        _all_filenames(args), config['files'], config['exclude'],
+    )
+    classifier = Classifier(filenames)
+    retval = 0
+    for hook in hooks:
+        retval |= _run_single_hook(
+            classifier, hook, skips, cols,
+            verbose=args.verbose, use_color=args.color,
+        )
+        if retval and config['fail_fast']:
+            break
+    if retval and args.show_diff_on_failure and git.has_diff():
+        if args.all_files:
+            output.write_line(
+                'pre-commit hook(s) made changes.\n'
+                'If you are seeing this message in CI, '
+                'reproduce locally with: `pre-commit run --all-files`.\n'
+                'To run `pre-commit` as part of git workflow, use '
+                '`pre-commit install`.',
+            )
+        output.write_line('All changes made by hooks:')
+        # args.color is a boolean.
+        # See user_color function in color.py
+        git_color_opt = 'always' if args.color else 'never'
+        subprocess.call((
+            'git', '--no-pager', 'diff', '--no-ext-diff',
+            f'--color={git_color_opt}',
+        ))
+
+    return retval
+
+
+def _has_unmerged_paths() -> bool:
+    _, stdout, _ = cmd_output_b('git', 'ls-files', '--unmerged')
+    return bool(stdout.strip())
+
+
+def _has_unstaged_config(config_file: str) -> bool:
+    retcode, _, _ = cmd_output_b(
+        'git', 'diff', '--no-ext-diff', '--exit-code', config_file,
+        retcode=None,
+    )
+    # be explicit, other git errors don't mean it has an unstaged config.
+    return retcode == 1
+
+
+def run(
+        config_file: str,
+        store: Store,
+        args: argparse.Namespace,
+        environ: EnvironT = os.environ,
+) -> int:
+    stash = not args.all_files and not args.files
+
+    # Check if we have unresolved merge conflict files and fail fast.
+    if _has_unmerged_paths():
+        logger.error('Unmerged files.  Resolve before committing.')
+        return 1
+    if bool(args.from_ref) != bool(args.to_ref):
+        logger.error('Specify both --from-ref and --to-ref.')
+        return 1
+    if stash and _has_unstaged_config(config_file):
+        logger.error(
+            f'Your pre-commit configuration is unstaged.\n'
+            f'`git add {config_file}` to fix this.',
+        )
+        return 1
+    if (
+            args.hook_stage in {'prepare-commit-msg', 'commit-msg'} and
+            not args.commit_msg_filename
+    ):
+        logger.error(
+            f'`--commit-msg-filename` is required for '
+            f'`--hook-stage {args.hook_stage}`',
+        )
+        return 1
+
+    # Expose from-ref / to-ref as environment variables for hooks to consume
+    if args.from_ref and args.to_ref:
+        # legacy names
+        environ['PRE_COMMIT_ORIGIN'] = args.from_ref
+        environ['PRE_COMMIT_SOURCE'] = args.to_ref
+        # new names
+        environ['PRE_COMMIT_FROM_REF'] = args.from_ref
+        environ['PRE_COMMIT_TO_REF'] = args.to_ref
+
+    if args.remote_name and args.remote_url:
+        environ['PRE_COMMIT_REMOTE_NAME'] = args.remote_name
+        environ['PRE_COMMIT_REMOTE_URL'] = args.remote_url
+
+    if args.checkout_type:
+        environ['PRE_COMMIT_CHECKOUT_TYPE'] = args.checkout_type
+
+    with contextlib.ExitStack() as exit_stack:
+        if stash:
+            exit_stack.enter_context(staged_files_only(store.directory))
+
+        config = load_config(config_file)
+        hooks = [
+            hook
+            for hook in all_hooks(config, store)
+            if not args.hook or hook.id == args.hook or hook.alias == args.hook
+            if args.hook_stage in hook.stages
+        ]
+
+        if args.hook and not hooks:
+            output.write_line(
+                f'No hook with id `{args.hook}` in stage `{args.hook_stage}`',
+            )
+            return 1
+
+        install_hook_envs(hooks, store)
+
+        return _run_hooks(config, hooks, args, environ)
+
+    # https://github.com/python/mypy/issues/7726
+    raise AssertionError('unreachable')
diff --git a/pre_commit/commands/sample_config.py b/pre_commit/commands/sample_config.py
new file mode 100644
index 0000000..d435faa
--- /dev/null
+++ b/pre_commit/commands/sample_config.py
@@ -0,0 +1,21 @@
+# TODO: maybe `git ls-remote git://github.com/pre-commit/pre-commit-hooks` to
+# determine the latest revision?  This adds ~200ms from my tests (and is
+# significantly faster than https:// or http://).  For now, periodically
+# manually updating the revision is fine.
+SAMPLE_CONFIG = '''\
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.4.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: check-added-large-files
+'''
+
+
+def sample_config() -> int:
+    print(SAMPLE_CONFIG, end='')
+    return 0
diff --git a/pre_commit/commands/try_repo.py b/pre_commit/commands/try_repo.py
new file mode 100644
index 0000000..4aee209
--- /dev/null
+++ b/pre_commit/commands/try_repo.py
@@ -0,0 +1,77 @@
+import argparse
+import logging
+import os.path
+from typing import Optional
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit import git
+from pre_commit import output
+from pre_commit.clientlib import load_manifest
+from pre_commit.commands.run import run
+from pre_commit.store import Store
+from pre_commit.util import cmd_output_b
+from pre_commit.util import tmpdir
+from pre_commit.util import yaml_dump
+from pre_commit.xargs import xargs
+
+logger = logging.getLogger(__name__)
+
+
+def _repo_ref(tmpdir: str, repo: str, ref: Optional[str]) -> Tuple[str, str]:
+    # if `ref` is explicitly passed, use it
+    if ref is not None:
+        return repo, ref
+
+    ref = git.head_rev(repo)
+    # if it exists on disk, we'll try and clone it with the local changes
+    if os.path.exists(repo) and git.has_diff('HEAD', repo=repo):
+        logger.warning('Creating temporary repo with uncommitted changes...')
+
+        shadow = os.path.join(tmpdir, 'shadow-repo')
+        cmd_output_b('git', 'clone', repo, shadow)
+        cmd_output_b('git', 'checkout', ref, '-b', '_pc_tmp', cwd=shadow)
+
+        idx = git.git_path('index', repo=shadow)
+        objs = git.git_path('objects', repo=shadow)
+        env = dict(os.environ, GIT_INDEX_FILE=idx, GIT_OBJECT_DIRECTORY=objs)
+
+        staged_files = git.get_staged_files(cwd=repo)
+        if staged_files:
+            xargs(('git', 'add', '--'), staged_files, cwd=repo, env=env)
+
+        cmd_output_b('git', 'add', '-u', cwd=repo, env=env)
+        git.commit(repo=shadow)
+
+        return shadow, git.head_rev(shadow)
+    else:
+        return repo, ref
+
+
+def try_repo(args: argparse.Namespace) -> int:
+    with tmpdir() as tempdir:
+        repo, ref = _repo_ref(tempdir, args.repo, args.ref)
+
+        store = Store(tempdir)
+        if args.hook:
+            hooks = [{'id': args.hook}]
+        else:
+            repo_path = store.clone(repo, ref)
+            manifest = load_manifest(os.path.join(repo_path, C.MANIFEST_FILE))
+            manifest = sorted(manifest, key=lambda hook: hook['id'])
+            hooks = [{'id': hook['id']} for hook in manifest]
+
+        config = {'repos': [{'repo': repo, 'rev': ref, 'hooks': hooks}]}
+        config_s = yaml_dump(config)
+
+        config_filename = os.path.join(tempdir, C.CONFIG_FILE)
+        with open(config_filename, 'w') as cfg:
+            cfg.write(config_s)
+
+        output.write_line('=' * 79)
+        output.write_line('Using config:')
+        output.write_line('=' * 79)
+        output.write(config_s)
+        output.write_line('=' * 79)
+
+        return run(config_filename, store, args)
diff --git a/pre_commit/constants.py b/pre_commit/constants.py
new file mode 100644
index 0000000..e2b8e3a
--- /dev/null
+++ b/pre_commit/constants.py
@@ -0,0 +1,24 @@
+import sys
+
+if sys.version_info < (3, 8):  # pragma: no cover (<PY38)
+    import importlib_metadata
+else:  # pragma: no cover (PY38+)
+    import importlib.metadata as importlib_metadata
+
+CONFIG_FILE = '.pre-commit-config.yaml'
+MANIFEST_FILE = '.pre-commit-hooks.yaml'
+
+# Bump when installation changes in a backwards / forwards incompatible way
+INSTALLED_STATE_VERSION = '1'
+# Bump when modifying `empty_template`
+LOCAL_REPO_VERSION = '1'
+
+VERSION = importlib_metadata.version('pre_commit')
+
+# `manual` is not invoked by any installed git hook.  See #719
+STAGES = (
+    'commit', 'merge-commit', 'prepare-commit-msg', 'commit-msg', 'manual',
+    'post-checkout', 'push',
+)
+
+DEFAULT = 'default'
diff --git a/pre_commit/envcontext.py b/pre_commit/envcontext.py
new file mode 100644
index 0000000..16d3d15
--- /dev/null
+++ b/pre_commit/envcontext.py
@@ -0,0 +1,67 @@
+import contextlib
+import enum
+import os
+from typing import Generator
+from typing import NamedTuple
+from typing import Optional
+from typing import Tuple
+from typing import Union
+
+from pre_commit.util import EnvironT
+
+
+class _Unset(enum.Enum):
+    UNSET = 1
+
+
+UNSET = _Unset.UNSET
+
+
+class Var(NamedTuple):
+    name: str
+    default: str = ''
+
+
+SubstitutionT = Tuple[Union[str, Var], ...]
+ValueT = Union[str, _Unset, SubstitutionT]
+PatchesT = Tuple[Tuple[str, ValueT], ...]
+
+
+def format_env(parts: SubstitutionT, env: EnvironT) -> str:
+    return ''.join(
+        env.get(part.name, part.default) if isinstance(part, Var) else part
+        for part in parts
+    )
+
+
+@contextlib.contextmanager
+def envcontext(
+        patch: PatchesT,
+        _env: Optional[EnvironT] = None,
+) -> Generator[None, None, None]:
+    """In this context, `os.environ` is modified according to `patch`.
+
+    `patch` is an iterable of 2-tuples (key, value):
+        `key`: string
+        `value`:
+            - string: `environ[key] == value` inside the context.
+            - UNSET: `key not in environ` inside the context.
+            - template: A template is a tuple of strings and Var which will be
+              replaced with the previous environment
+    """
+    env = os.environ if _env is None else _env
+    before = env.copy()
+
+    for k, v in patch:
+        if v is UNSET:
+            env.pop(k, None)
+        elif isinstance(v, tuple):
+            env[k] = format_env(v, before)
+        else:
+            env[k] = v
+
+    try:
+        yield
+    finally:
+        env.clear()
+        env.update(before)
diff --git a/pre_commit/error_handler.py b/pre_commit/error_handler.py
new file mode 100644
index 0000000..b2321ae
--- /dev/null
+++ b/pre_commit/error_handler.py
@@ -0,0 +1,64 @@
+import contextlib
+import functools
+import os.path
+import sys
+import traceback
+from typing import Generator
+
+import pre_commit.constants as C
+from pre_commit import output
+from pre_commit.store import Store
+from pre_commit.util import force_bytes
+
+
+class FatalError(RuntimeError):
+    pass
+
+
+def _log_and_exit(msg: str, exc: BaseException, formatted: str) -> None:
+    error_msg = f'{msg}: {type(exc).__name__}: '.encode() + force_bytes(exc)
+    output.write_line_b(error_msg)
+    log_path = os.path.join(Store().directory, 'pre-commit.log')
+    output.write_line(f'Check the log at {log_path}')
+
+    with open(log_path, 'wb') as log:
+        _log_line = functools.partial(output.write_line, stream=log)
+        _log_line_b = functools.partial(output.write_line_b, stream=log)
+
+        _log_line('### version information')
+        _log_line()
+        _log_line('```')
+        _log_line(f'pre-commit version: {C.VERSION}')
+        _log_line('sys.version:')
+        for line in sys.version.splitlines():
+            _log_line(f'    {line}')
+        _log_line(f'sys.executable: {sys.executable}')
+        _log_line(f'os.name: {os.name}')
+        _log_line(f'sys.platform: {sys.platform}')
+        _log_line('```')
+        _log_line()
+
+        _log_line('### error information')
+        _log_line()
+        _log_line('```')
+        _log_line_b(error_msg)
+        _log_line('```')
+        _log_line()
+        _log_line('```')
+        _log_line(formatted)
+        _log_line('```')
+    raise SystemExit(1)
+
+
+@contextlib.contextmanager
+def error_handler() -> Generator[None, None, None]:
+    try:
+        yield
+    except (Exception, KeyboardInterrupt) as e:
+        if isinstance(e, FatalError):
+            msg = 'An error has occurred'
+        elif isinstance(e, KeyboardInterrupt):
+            msg = 'Interrupted (^C)'
+        else:
+            msg = 'An unexpected error has occurred'
+        _log_and_exit(msg, e, traceback.format_exc())
diff --git a/pre_commit/file_lock.py b/pre_commit/file_lock.py
new file mode 100644
index 0000000..ff0dc5e
--- /dev/null
+++ b/pre_commit/file_lock.py
@@ -0,0 +1,76 @@
+import contextlib
+import errno
+import os
+from typing import Callable
+from typing import Generator
+
+
+if os.name == 'nt':  # pragma: no cover (windows)
+    import msvcrt
+
+    # https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/locking
+
+    # on windows we lock "regions" of files, we don't care about the actual
+    # byte region so we'll just pick *some* number here.
+    _region = 0xffff
+
+    @contextlib.contextmanager
+    def _locked(
+            fileno: int,
+            blocked_cb: Callable[[], None],
+    ) -> Generator[None, None, None]:
+        try:
+            # TODO: https://github.com/python/typeshed/pull/3607
+            msvcrt.locking(fileno, msvcrt.LK_NBLCK, _region)  # type: ignore
+        except OSError:
+            blocked_cb()
+            while True:
+                try:
+                    # TODO: https://github.com/python/typeshed/pull/3607
+                    msvcrt.locking(fileno, msvcrt.LK_LOCK, _region)  # type: ignore  # noqa: E501
+                except OSError as e:
+                    # Locking violation. Returned when the _LK_LOCK or _LK_RLCK
+                    # flag is specified and the file cannot be locked after 10
+                    # attempts.
+                    if e.errno != errno.EDEADLOCK:
+                        raise
+                else:
+                    break
+
+        try:
+            yield
+        finally:
+            # From cursory testing, it seems to get unlocked when the file is
+            # closed so this may not be necessary.
+            # The documentation however states:
+            # "Regions should be locked only briefly and should be unlocked
+            # before closing a file or exiting the program."
+            # TODO: https://github.com/python/typeshed/pull/3607
+            msvcrt.locking(fileno, msvcrt.LK_UNLCK, _region)  # type: ignore
+else:  # pragma: win32 no cover
+    import fcntl
+
+    @contextlib.contextmanager
+    def _locked(
+            fileno: int,
+            blocked_cb: Callable[[], None],
+    ) -> Generator[None, None, None]:
+        try:
+            fcntl.flock(fileno, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        except OSError:  # pragma: no cover (tests are single-threaded)
+            blocked_cb()
+            fcntl.flock(fileno, fcntl.LOCK_EX)
+        try:
+            yield
+        finally:
+            fcntl.flock(fileno, fcntl.LOCK_UN)
+
+
+@contextlib.contextmanager
+def lock(
+        path: str,
+        blocked_cb: Callable[[], None],
+) -> Generator[None, None, None]:
+    with open(path, 'a+') as f:
+        with _locked(f.fileno(), blocked_cb):
+            yield
diff --git a/pre_commit/git.py b/pre_commit/git.py
new file mode 100644
index 0000000..7e757f2
--- /dev/null
+++ b/pre_commit/git.py
@@ -0,0 +1,196 @@
+import logging
+import os.path
+import sys
+from typing import Dict
+from typing import List
+from typing import Optional
+from typing import Set
+
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+from pre_commit.util import EnvironT
+
+
+logger = logging.getLogger(__name__)
+
+
+def zsplit(s: str) -> List[str]:
+    s = s.strip('\0')
+    if s:
+        return s.split('\0')
+    else:
+        return []
+
+
+def no_git_env(_env: Optional[EnvironT] = None) -> Dict[str, str]:
+    # Too many bugs dealing with environment variables and GIT:
+    # https://github.com/pre-commit/pre-commit/issues/300
+    # In git 2.6.3 (maybe others), git exports GIT_WORK_TREE while running
+    # pre-commit hooks
+    # In git 1.9.1 (maybe others), git exports GIT_DIR and GIT_INDEX_FILE
+    # while running pre-commit hooks in submodules.
+    # GIT_DIR: Causes git clone to clone wrong thing
+    # GIT_INDEX_FILE: Causes 'error invalid object ...' during commit
+    _env = _env if _env is not None else os.environ
+    return {
+        k: v for k, v in _env.items()
+        if not k.startswith('GIT_') or
+        k in {
+            'GIT_EXEC_PATH', 'GIT_SSH', 'GIT_SSH_COMMAND', 'GIT_SSL_CAINFO',
+            'GIT_SSL_NO_VERIFY',
+        }
+    }
+
+
+def get_root() -> str:
+    return cmd_output('git', 'rev-parse', '--show-toplevel')[1].strip()
+
+
+def get_git_dir(git_root: str = '.') -> str:
+    opts = ('--git-common-dir', '--git-dir')
+    _, out, _ = cmd_output('git', 'rev-parse', *opts, cwd=git_root)
+    for line, opt in zip(out.splitlines(), opts):
+        if line != opt:  # pragma: no branch (git < 2.5)
+            return os.path.normpath(os.path.join(git_root, line))
+    else:
+        raise AssertionError('unreachable: no git dir')
+
+
+def get_remote_url(git_root: str) -> str:
+    _, out, _ = cmd_output('git', 'config', 'remote.origin.url', cwd=git_root)
+    return out.strip()
+
+
+def is_in_merge_conflict() -> bool:
+    git_dir = get_git_dir('.')
+    return (
+        os.path.exists(os.path.join(git_dir, 'MERGE_MSG')) and
+        os.path.exists(os.path.join(git_dir, 'MERGE_HEAD'))
+    )
+
+
+def parse_merge_msg_for_conflicts(merge_msg: bytes) -> List[str]:
+    # Conflicted files start with tabs
+    return [
+        line.lstrip(b'#').strip().decode()
+        for line in merge_msg.splitlines()
+        # '#\t' for git 2.4.1
+        if line.startswith((b'\t', b'#\t'))
+    ]
+
+
+def get_conflicted_files() -> Set[str]:
+    logger.info('Checking merge-conflict files only.')
+    # Need to get the conflicted files from the MERGE_MSG because they could
+    # have resolved the conflict by choosing one side or the other
+    with open(os.path.join(get_git_dir('.'), 'MERGE_MSG'), 'rb') as f:
+        merge_msg = f.read()
+    merge_conflict_filenames = parse_merge_msg_for_conflicts(merge_msg)
+
+    # This will get the rest of the changes made after the merge.
+    # If they resolved the merge conflict by choosing a mesh of both sides
+    # this will also include the conflicted files
+    tree_hash = cmd_output('git', 'write-tree')[1].strip()
+    merge_diff_filenames = zsplit(
+        cmd_output(
+            'git', 'diff', '--name-only', '--no-ext-diff', '-z',
+            '-m', tree_hash, 'HEAD', 'MERGE_HEAD',
+        )[1],
+    )
+    return set(merge_conflict_filenames) | set(merge_diff_filenames)
+
+
+def get_staged_files(cwd: Optional[str] = None) -> List[str]:
+    return zsplit(
+        cmd_output(
+            'git', 'diff', '--staged', '--name-only', '--no-ext-diff', '-z',
+            # Everything except for D
+            '--diff-filter=ACMRTUXB',
+            cwd=cwd,
+        )[1],
+    )
+
+
+def intent_to_add_files() -> List[str]:
+    _, stdout, _ = cmd_output('git', 'status', '--porcelain', '-z')
+    parts = list(reversed(zsplit(stdout)))
+    intent_to_add = []
+    while parts:
+        line = parts.pop()
+        status, filename = line[:3], line[3:]
+        if status[0] in {'C', 'R'}:  # renames / moves have an additional arg
+            parts.pop()
+        if status[1] == 'A':
+            intent_to_add.append(filename)
+    return intent_to_add
+
+
+def get_all_files() -> List[str]:
+    return zsplit(cmd_output('git', 'ls-files', '-z')[1])
+
+
+def get_changed_files(old: str, new: str) -> List[str]:
+    return zsplit(
+        cmd_output(
+            'git', 'diff', '--name-only', '--no-ext-diff', '-z',
+            f'{old}...{new}',
+        )[1],
+    )
+
+
+def head_rev(remote: str) -> str:
+    _, out, _ = cmd_output('git', 'ls-remote', '--exit-code', remote, 'HEAD')
+    return out.split()[0]
+
+
+def has_diff(*args: str, repo: str = '.') -> bool:
+    cmd = ('git', 'diff', '--quiet', '--no-ext-diff', *args)
+    return cmd_output_b(*cmd, cwd=repo, retcode=None)[0] == 1
+
+
+def has_core_hookpaths_set() -> bool:
+    _, out, _ = cmd_output_b('git', 'config', 'core.hooksPath', retcode=None)
+    return bool(out.strip())
+
+
+def init_repo(path: str, remote: str) -> None:
+    if os.path.isdir(remote):
+        remote = os.path.abspath(remote)
+
+    env = no_git_env()
+    cmd_output_b('git', 'init', path, env=env)
+    cmd_output_b('git', 'remote', 'add', 'origin', remote, cwd=path, env=env)
+
+
+def commit(repo: str = '.') -> None:
+    env = no_git_env()
+    name, email = 'pre-commit', 'asottile+pre-commit@umich.edu'
+    env['GIT_AUTHOR_NAME'] = env['GIT_COMMITTER_NAME'] = name
+    env['GIT_AUTHOR_EMAIL'] = env['GIT_COMMITTER_EMAIL'] = email
+    cmd = ('git', 'commit', '--no-edit', '--no-gpg-sign', '-n', '-minit')
+    cmd_output_b(*cmd, cwd=repo, env=env)
+
+
+def git_path(name: str, repo: str = '.') -> str:
+    _, out, _ = cmd_output('git', 'rev-parse', '--git-path', name, cwd=repo)
+    return os.path.join(repo, out.strip())
+
+
+def check_for_cygwin_mismatch() -> None:
+    """See https://github.com/pre-commit/pre-commit/issues/354"""
+    if sys.platform in ('cygwin', 'win32'):  # pragma: no cover (windows)
+        is_cygwin_python = sys.platform == 'cygwin'
+        toplevel = cmd_output('git', 'rev-parse', '--show-toplevel')[1]
+        is_cygwin_git = toplevel.startswith('/')
+
+        if is_cygwin_python ^ is_cygwin_git:
+            exe_type = {True: '(cygwin)', False: '(windows)'}
+            logger.warn(
+                f'pre-commit has detected a mix of cygwin python / git\n'
+                f'This combination is not supported, it is likely you will '
+                f'receive an error later in the program.\n'
+                f'Make sure to use cygwin git+python while using cygwin\n'
+                f'These can be installed through the cygwin installer.\n'
+                f' - python {exe_type[is_cygwin_python]}\n'
+                f' - git {exe_type[is_cygwin_git]}\n',
+            )
diff --git a/pre_commit/hook.py b/pre_commit/hook.py
new file mode 100644
index 0000000..b65ac42
--- /dev/null
+++ b/pre_commit/hook.py
@@ -0,0 +1,63 @@
+import logging
+import shlex
+from typing import Any
+from typing import Dict
+from typing import NamedTuple
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.prefix import Prefix
+
+logger = logging.getLogger('pre_commit')
+
+
+class Hook(NamedTuple):
+    src: str
+    prefix: Prefix
+    id: str
+    name: str
+    entry: str
+    language: str
+    alias: str
+    files: str
+    exclude: str
+    types: Sequence[str]
+    exclude_types: Sequence[str]
+    additional_dependencies: Sequence[str]
+    args: Sequence[str]
+    always_run: bool
+    pass_filenames: bool
+    description: str
+    language_version: str
+    log_file: str
+    minimum_pre_commit_version: str
+    require_serial: bool
+    stages: Sequence[str]
+    verbose: bool
+
+    @property
+    def cmd(self) -> Tuple[str, ...]:
+        return (*shlex.split(self.entry), *self.args)
+
+    @property
+    def install_key(self) -> Tuple[Prefix, str, str, Tuple[str, ...]]:
+        return (
+            self.prefix,
+            self.language,
+            self.language_version,
+            tuple(self.additional_dependencies),
+        )
+
+    @classmethod
+    def create(cls, src: str, prefix: Prefix, dct: Dict[str, Any]) -> 'Hook':
+        # TODO: have cfgv do this (?)
+        extra_keys = set(dct) - _KEYS
+        if extra_keys:
+            logger.warning(
+                f'Unexpected key(s) present on {src} => {dct["id"]}: '
+                f'{", ".join(sorted(extra_keys))}',
+            )
+        return cls(src=src, prefix=prefix, **{k: dct[k] for k in _KEYS})
+
+
+_KEYS = frozenset(set(Hook._fields) - {'src', 'prefix'})
diff --git a/pre_commit/languages/__init__.py b/pre_commit/languages/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/pre_commit/languages/__init__.py
diff --git a/pre_commit/languages/all.py b/pre_commit/languages/all.py
new file mode 100644
index 0000000..8f4ffa8
--- /dev/null
+++ b/pre_commit/languages/all.py
@@ -0,0 +1,60 @@
+from typing import Callable
+from typing import NamedTuple
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.hook import Hook
+from pre_commit.languages import conda
+from pre_commit.languages import docker
+from pre_commit.languages import docker_image
+from pre_commit.languages import fail
+from pre_commit.languages import golang
+from pre_commit.languages import node
+from pre_commit.languages import perl
+from pre_commit.languages import pygrep
+from pre_commit.languages import python
+from pre_commit.languages import python_venv
+from pre_commit.languages import ruby
+from pre_commit.languages import rust
+from pre_commit.languages import script
+from pre_commit.languages import swift
+from pre_commit.languages import system
+from pre_commit.prefix import Prefix
+
+
+class Language(NamedTuple):
+    name: str
+    # Use `None` for no installation / environment
+    ENVIRONMENT_DIR: Optional[str]
+    # return a value to replace `'default` for `language_version`
+    get_default_version: Callable[[], str]
+    # return whether the environment is healthy (or should be rebuilt)
+    healthy: Callable[[Prefix, str], bool]
+    # install a repository for the given language and language_version
+    install_environment: Callable[[Prefix, str, Sequence[str]], None]
+    # execute a hook and return the exit code and output
+    run_hook: 'Callable[[Hook, Sequence[str], bool], Tuple[int, bytes]]'
+
+
+# TODO: back to modules + Protocol: https://github.com/python/mypy/issues/5018
+languages = {
+    # BEGIN GENERATED (testing/gen-languages-all)
+    'conda': Language(name='conda', ENVIRONMENT_DIR=conda.ENVIRONMENT_DIR, get_default_version=conda.get_default_version, healthy=conda.healthy, install_environment=conda.install_environment, run_hook=conda.run_hook),  # noqa: E501
+    'docker': Language(name='docker', ENVIRONMENT_DIR=docker.ENVIRONMENT_DIR, get_default_version=docker.get_default_version, healthy=docker.healthy, install_environment=docker.install_environment, run_hook=docker.run_hook),  # noqa: E501
+    'docker_image': Language(name='docker_image', ENVIRONMENT_DIR=docker_image.ENVIRONMENT_DIR, get_default_version=docker_image.get_default_version, healthy=docker_image.healthy, install_environment=docker_image.install_environment, run_hook=docker_image.run_hook),  # noqa: E501
+    'fail': Language(name='fail', ENVIRONMENT_DIR=fail.ENVIRONMENT_DIR, get_default_version=fail.get_default_version, healthy=fail.healthy, install_environment=fail.install_environment, run_hook=fail.run_hook),  # noqa: E501
+    'golang': Language(name='golang', ENVIRONMENT_DIR=golang.ENVIRONMENT_DIR, get_default_version=golang.get_default_version, healthy=golang.healthy, install_environment=golang.install_environment, run_hook=golang.run_hook),  # noqa: E501
+    'node': Language(name='node', ENVIRONMENT_DIR=node.ENVIRONMENT_DIR, get_default_version=node.get_default_version, healthy=node.healthy, install_environment=node.install_environment, run_hook=node.run_hook),  # noqa: E501
+    'perl': Language(name='perl', ENVIRONMENT_DIR=perl.ENVIRONMENT_DIR, get_default_version=perl.get_default_version, healthy=perl.healthy, install_environment=perl.install_environment, run_hook=perl.run_hook),  # noqa: E501
+    'pygrep': Language(name='pygrep', ENVIRONMENT_DIR=pygrep.ENVIRONMENT_DIR, get_default_version=pygrep.get_default_version, healthy=pygrep.healthy, install_environment=pygrep.install_environment, run_hook=pygrep.run_hook),  # noqa: E501
+    'python': Language(name='python', ENVIRONMENT_DIR=python.ENVIRONMENT_DIR, get_default_version=python.get_default_version, healthy=python.healthy, install_environment=python.install_environment, run_hook=python.run_hook),  # noqa: E501
+    'python_venv': Language(name='python_venv', ENVIRONMENT_DIR=python_venv.ENVIRONMENT_DIR, get_default_version=python_venv.get_default_version, healthy=python_venv.healthy, install_environment=python_venv.install_environment, run_hook=python_venv.run_hook),  # noqa: E501
+    'ruby': Language(name='ruby', ENVIRONMENT_DIR=ruby.ENVIRONMENT_DIR, get_default_version=ruby.get_default_version, healthy=ruby.healthy, install_environment=ruby.install_environment, run_hook=ruby.run_hook),  # noqa: E501
+    'rust': Language(name='rust', ENVIRONMENT_DIR=rust.ENVIRONMENT_DIR, get_default_version=rust.get_default_version, healthy=rust.healthy, install_environment=rust.install_environment, run_hook=rust.run_hook),  # noqa: E501
+    'script': Language(name='script', ENVIRONMENT_DIR=script.ENVIRONMENT_DIR, get_default_version=script.get_default_version, healthy=script.healthy, install_environment=script.install_environment, run_hook=script.run_hook),  # noqa: E501
+    'swift': Language(name='swift', ENVIRONMENT_DIR=swift.ENVIRONMENT_DIR, get_default_version=swift.get_default_version, healthy=swift.healthy, install_environment=swift.install_environment, run_hook=swift.run_hook),  # noqa: E501
+    'system': Language(name='system', ENVIRONMENT_DIR=system.ENVIRONMENT_DIR, get_default_version=system.get_default_version, healthy=system.healthy, install_environment=system.install_environment, run_hook=system.run_hook),  # noqa: E501
+    # END GENERATED
+}
+all_languages = sorted(languages)
diff --git a/pre_commit/languages/conda.py b/pre_commit/languages/conda.py
new file mode 100644
index 0000000..071757a
--- /dev/null
+++ b/pre_commit/languages/conda.py
@@ -0,0 +1,84 @@
+import contextlib
+import os
+from typing import Generator
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import SubstitutionT
+from pre_commit.envcontext import UNSET
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'conda'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def get_env_patch(env: str) -> PatchesT:
+    # On non-windows systems executable live in $CONDA_PREFIX/bin, on Windows
+    # they can be in $CONDA_PREFIX/bin, $CONDA_PREFIX/Library/bin,
+    # $CONDA_PREFIX/Scripts and $CONDA_PREFIX. Whereas the latter only
+    # seems to be used for python.exe.
+    path: SubstitutionT = (os.path.join(env, 'bin'), os.pathsep, Var('PATH'))
+    if os.name == 'nt':  # pragma: no cover (platform specific)
+        path = (env, os.pathsep, *path)
+        path = (os.path.join(env, 'Scripts'), os.pathsep, *path)
+        path = (os.path.join(env, 'Library', 'bin'), os.pathsep, *path)
+
+    return (
+        ('PYTHONHOME', UNSET),
+        ('VIRTUAL_ENV', UNSET),
+        ('CONDA_PREFIX', env),
+        ('PATH', path),
+    )
+
+
+@contextlib.contextmanager
+def in_env(
+        prefix: Prefix,
+        language_version: str,
+) -> Generator[None, None, None]:
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, language_version)
+    envdir = prefix.path(directory)
+    with envcontext(get_env_patch(envdir)):
+        yield
+
+
+def install_environment(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> None:
+    helpers.assert_version_default('conda', version)
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
+
+    env_dir = prefix.path(directory)
+    with clean_path_on_failure(env_dir):
+        cmd_output_b(
+            'conda', 'env', 'create', '-p', env_dir, '--file',
+            'environment.yml', cwd=prefix.prefix_dir,
+        )
+        if additional_dependencies:
+            cmd_output_b(
+                'conda', 'install', '-p', env_dir, *additional_dependencies,
+                cwd=prefix.prefix_dir,
+            )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    # TODO: Some rare commands need to be run using `conda run` but mostly we
+    #       can run them withot which is much quicker and produces a better
+    #       output.
+    # cmd = ('conda', 'run', '-p', env_dir) + hook.cmd
+    with in_env(hook.prefix, hook.language_version):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/docker.py b/pre_commit/languages/docker.py
new file mode 100644
index 0000000..f449584
--- /dev/null
+++ b/pre_commit/languages/docker.py
@@ -0,0 +1,114 @@
+import hashlib
+import os
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import CalledProcessError
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'docker'
+PRE_COMMIT_LABEL = 'PRE_COMMIT'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def md5(s: str) -> str:  # pragma: win32 no cover
+    return hashlib.md5(s.encode()).hexdigest()
+
+
+def docker_tag(prefix: Prefix) -> str:  # pragma: win32 no cover
+    md5sum = md5(os.path.basename(prefix.prefix_dir)).lower()
+    return f'pre-commit-{md5sum}'
+
+
+def docker_is_running() -> bool:  # pragma: win32 no cover
+    try:
+        cmd_output_b('docker', 'ps')
+    except CalledProcessError:
+        return False
+    else:
+        return True
+
+
+def assert_docker_available() -> None:  # pragma: win32 no cover
+    assert docker_is_running(), (
+        'Docker is either not running or not configured in this environment'
+    )
+
+
+def build_docker_image(
+        prefix: Prefix,
+        *,
+        pull: bool,
+) -> None:  # pragma: win32 no cover
+    cmd: Tuple[str, ...] = (
+        'docker', 'build',
+        '--tag', docker_tag(prefix),
+        '--label', PRE_COMMIT_LABEL,
+    )
+    if pull:
+        cmd += ('--pull',)
+    # This must come last for old versions of docker.  See #477
+    cmd += ('.',)
+    helpers.run_setup_cmd(prefix, cmd)
+
+
+def install_environment(
+        prefix: Prefix, version: str, additional_dependencies: Sequence[str],
+) -> None:  # pragma: win32 no cover
+    helpers.assert_version_default('docker', version)
+    helpers.assert_no_additional_deps('docker', additional_dependencies)
+    assert_docker_available()
+
+    directory = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+
+    # Docker doesn't really have relevant disk environment, but pre-commit
+    # still needs to cleanup its state files on failure
+    with clean_path_on_failure(directory):
+        build_docker_image(prefix, pull=True)
+        os.mkdir(directory)
+
+
+def get_docker_user() -> str:  # pragma: win32 no cover
+    try:
+        return f'{os.getuid()}:{os.getgid()}'
+    except AttributeError:
+        return '1000:1000'
+
+
+def docker_cmd() -> Tuple[str, ...]:  # pragma: win32 no cover
+    return (
+        'docker', 'run',
+        '--rm',
+        '-u', get_docker_user(),
+        # https://docs.docker.com/engine/reference/commandline/run/#mount-volumes-from-container-volumes-from
+        # The `Z` option tells Docker to label the content with a private
+        # unshared label. Only the current container can use a private volume.
+        '-v', f'{os.getcwd()}:/src:rw,Z',
+        '--workdir', '/src',
+    )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:  # pragma: win32 no cover
+    assert_docker_available()
+    # Rebuild the docker image in case it has gone missing, as many people do
+    # automated cleanup of docker images.
+    build_docker_image(hook.prefix, pull=False)
+
+    hook_cmd = hook.cmd
+    entry_exe, cmd_rest = hook.cmd[0], hook_cmd[1:]
+
+    entry_tag = ('--entrypoint', entry_exe, docker_tag(hook.prefix))
+    cmd = docker_cmd() + entry_tag + cmd_rest
+    return helpers.run_xargs(hook, cmd, file_args, color=color)
diff --git a/pre_commit/languages/docker_image.py b/pre_commit/languages/docker_image.py
new file mode 100644
index 0000000..0c51df6
--- /dev/null
+++ b/pre_commit/languages/docker_image.py
@@ -0,0 +1,22 @@
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.languages.docker import assert_docker_available
+from pre_commit.languages.docker import docker_cmd
+
+ENVIRONMENT_DIR = None
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+install_environment = helpers.no_install
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:  # pragma: win32 no cover
+    assert_docker_available()
+    cmd = docker_cmd() + hook.cmd
+    return helpers.run_xargs(hook, cmd, file_args, color=color)
diff --git a/pre_commit/languages/fail.py b/pre_commit/languages/fail.py
new file mode 100644
index 0000000..d2b02d2
--- /dev/null
+++ b/pre_commit/languages/fail.py
@@ -0,0 +1,20 @@
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+
+ENVIRONMENT_DIR = None
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+install_environment = helpers.no_install
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    out = f'{hook.entry}\n\n'.encode()
+    out += b'\n'.join(f.encode() for f in file_args) + b'\n'
+    return 1, out
diff --git a/pre_commit/languages/golang.py b/pre_commit/languages/golang.py
new file mode 100644
index 0000000..91ade1e
--- /dev/null
+++ b/pre_commit/languages/golang.py
@@ -0,0 +1,97 @@
+import contextlib
+import os.path
+import sys
+from typing import Generator
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit import git
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+from pre_commit.util import rmtree
+
+ENVIRONMENT_DIR = 'golangenv'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def get_env_patch(venv: str) -> PatchesT:
+    return (
+        ('PATH', (os.path.join(venv, 'bin'), os.pathsep, Var('PATH'))),
+    )
+
+
+@contextlib.contextmanager
+def in_env(prefix: Prefix) -> Generator[None, None, None]:
+    envdir = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+    with envcontext(get_env_patch(envdir)):
+        yield
+
+
+def guess_go_dir(remote_url: str) -> str:
+    if remote_url.endswith('.git'):
+        remote_url = remote_url[:-1 * len('.git')]
+    looks_like_url = (
+        not remote_url.startswith('file://') and
+        ('//' in remote_url or '@' in remote_url)
+    )
+    remote_url = remote_url.replace(':', '/')
+    if looks_like_url:
+        _, _, remote_url = remote_url.rpartition('//')
+        _, _, remote_url = remote_url.rpartition('@')
+        return remote_url
+    else:
+        return 'unknown_src_dir'
+
+
+def install_environment(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> None:
+    helpers.assert_version_default('golang', version)
+    directory = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+
+    with clean_path_on_failure(directory):
+        remote = git.get_remote_url(prefix.prefix_dir)
+        repo_src_dir = os.path.join(directory, 'src', guess_go_dir(remote))
+
+        # Clone into the goenv we'll create
+        helpers.run_setup_cmd(prefix, ('git', 'clone', '.', repo_src_dir))
+
+        if sys.platform == 'cygwin':  # pragma: no cover
+            _, gopath, _ = cmd_output('cygpath', '-w', directory)
+            gopath = gopath.strip()
+        else:
+            gopath = directory
+        env = dict(os.environ, GOPATH=gopath)
+        env.pop('GOBIN', None)
+        cmd_output_b('go', 'get', './...', cwd=repo_src_dir, env=env)
+        for dependency in additional_dependencies:
+            cmd_output_b('go', 'get', dependency, cwd=repo_src_dir, env=env)
+        # Same some disk space, we don't need these after installation
+        rmtree(prefix.path(directory, 'src'))
+        pkgdir = prefix.path(directory, 'pkg')
+        if os.path.exists(pkgdir):  # pragma: no cover (go<1.10)
+            rmtree(pkgdir)
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    with in_env(hook.prefix):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/helpers.py b/pre_commit/languages/helpers.py
new file mode 100644
index 0000000..b5c95e5
--- /dev/null
+++ b/pre_commit/languages/helpers.py
@@ -0,0 +1,109 @@
+import multiprocessing
+import os
+import random
+from typing import Any
+from typing import List
+from typing import Optional
+from typing import overload
+from typing import Sequence
+from typing import Tuple
+from typing import TYPE_CHECKING
+
+import pre_commit.constants as C
+from pre_commit.hook import Hook
+from pre_commit.prefix import Prefix
+from pre_commit.util import cmd_output_b
+from pre_commit.xargs import xargs
+
+if TYPE_CHECKING:
+    from typing import NoReturn
+
+FIXED_RANDOM_SEED = 1542676186
+
+
+def run_setup_cmd(prefix: Prefix, cmd: Tuple[str, ...]) -> None:
+    cmd_output_b(*cmd, cwd=prefix.prefix_dir)
+
+
+@overload
+def environment_dir(d: None, language_version: str) -> None: ...
+@overload
+def environment_dir(d: str, language_version: str) -> str: ...
+
+
+def environment_dir(d: Optional[str], language_version: str) -> Optional[str]:
+    if d is None:
+        return None
+    else:
+        return f'{d}-{language_version}'
+
+
+def assert_version_default(binary: str, version: str) -> None:
+    if version != C.DEFAULT:
+        raise AssertionError(
+            f'For now, pre-commit requires system-installed {binary}',
+        )
+
+
+def assert_no_additional_deps(
+        lang: str,
+        additional_deps: Sequence[str],
+) -> None:
+    if additional_deps:
+        raise AssertionError(
+            f'For now, pre-commit does not support '
+            f'additional_dependencies for {lang}',
+        )
+
+
+def basic_get_default_version() -> str:
+    return C.DEFAULT
+
+
+def basic_healthy(prefix: Prefix, language_version: str) -> bool:
+    return True
+
+
+def no_install(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> 'NoReturn':
+    raise AssertionError('This type is not installable')
+
+
+def target_concurrency(hook: Hook) -> int:
+    if hook.require_serial or 'PRE_COMMIT_NO_CONCURRENCY' in os.environ:
+        return 1
+    else:
+        # Travis appears to have a bunch of CPUs, but we can't use them all.
+        if 'TRAVIS' in os.environ:
+            return 2
+        else:
+            try:
+                return multiprocessing.cpu_count()
+            except NotImplementedError:
+                return 1
+
+
+def _shuffled(seq: Sequence[str]) -> List[str]:
+    """Deterministically shuffle"""
+    fixed_random = random.Random()
+    fixed_random.seed(FIXED_RANDOM_SEED, version=1)
+
+    seq = list(seq)
+    random.shuffle(seq, random=fixed_random.random)
+    return seq
+
+
+def run_xargs(
+        hook: Hook,
+        cmd: Tuple[str, ...],
+        file_args: Sequence[str],
+        **kwargs: Any,
+) -> Tuple[int, bytes]:
+    # Shuffle the files so that they more evenly fill out the xargs partitions,
+    # but do it deterministically in case a hook cares about ordering.
+    file_args = _shuffled(file_args)
+    kwargs['target_concurrency'] = target_concurrency(hook)
+    return xargs(cmd, file_args, **kwargs)
diff --git a/pre_commit/languages/node.py b/pre_commit/languages/node.py
new file mode 100644
index 0000000..79ff807
--- /dev/null
+++ b/pre_commit/languages/node.py
@@ -0,0 +1,93 @@
+import contextlib
+import os
+import sys
+from typing import Generator
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.languages.python import bin_dir
+from pre_commit.prefix import Prefix
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'node_env'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def _envdir(prefix: Prefix, version: str) -> str:
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
+    return prefix.path(directory)
+
+
+def get_env_patch(venv: str) -> PatchesT:
+    if sys.platform == 'cygwin':  # pragma: no cover
+        _, win_venv, _ = cmd_output('cygpath', '-w', venv)
+        install_prefix = fr'{win_venv.strip()}\bin'
+        lib_dir = 'lib'
+    elif sys.platform == 'win32':  # pragma: no cover
+        install_prefix = bin_dir(venv)
+        lib_dir = 'Scripts'
+    else:  # pragma: win32 no cover
+        install_prefix = venv
+        lib_dir = 'lib'
+    return (
+        ('NODE_VIRTUAL_ENV', venv),
+        ('NPM_CONFIG_PREFIX', install_prefix),
+        ('npm_config_prefix', install_prefix),
+        ('NODE_PATH', os.path.join(venv, lib_dir, 'node_modules')),
+        ('PATH', (bin_dir(venv), os.pathsep, Var('PATH'))),
+    )
+
+
+@contextlib.contextmanager
+def in_env(
+        prefix: Prefix,
+        language_version: str,
+) -> Generator[None, None, None]:
+    with envcontext(get_env_patch(_envdir(prefix, language_version))):
+        yield
+
+
+def install_environment(
+        prefix: Prefix, version: str, additional_dependencies: Sequence[str],
+) -> None:
+    additional_dependencies = tuple(additional_dependencies)
+    assert prefix.exists('package.json')
+    envdir = _envdir(prefix, version)
+
+    # https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx?f=255&MSPPError=-2147217396#maxpath
+    if sys.platform == 'win32':  # pragma: no cover
+        envdir = f'\\\\?\\{os.path.normpath(envdir)}'
+    with clean_path_on_failure(envdir):
+        cmd = [
+            sys.executable, '-mnodeenv', '--prebuilt', '--clean-src', envdir,
+        ]
+        if version != C.DEFAULT:
+            cmd.extend(['-n', version])
+        cmd_output_b(*cmd)
+
+        with in_env(prefix, version):
+            # https://npm.community/t/npm-install-g-git-vs-git-clone-cd-npm-install-g/5449
+            # install as if we installed from git
+            helpers.run_setup_cmd(prefix, ('npm', 'install'))
+            helpers.run_setup_cmd(
+                prefix,
+                ('npm', 'install', '-g', '.', *additional_dependencies),
+            )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    with in_env(hook.prefix, hook.language_version):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/perl.py b/pre_commit/languages/perl.py
new file mode 100644
index 0000000..bbf5504
--- /dev/null
+++ b/pre_commit/languages/perl.py
@@ -0,0 +1,67 @@
+import contextlib
+import os
+import shlex
+from typing import Generator
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import clean_path_on_failure
+
+ENVIRONMENT_DIR = 'perl_env'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def _envdir(prefix: Prefix, version: str) -> str:
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
+    return prefix.path(directory)
+
+
+def get_env_patch(venv: str) -> PatchesT:
+    return (
+        ('PATH', (os.path.join(venv, 'bin'), os.pathsep, Var('PATH'))),
+        ('PERL5LIB', os.path.join(venv, 'lib', 'perl5')),
+        ('PERL_MB_OPT', f'--install_base {shlex.quote(venv)}'),
+        (
+            'PERL_MM_OPT', (
+                f'INSTALL_BASE={shlex.quote(venv)} '
+                f'INSTALLSITEMAN1DIR=none INSTALLSITEMAN3DIR=none'
+            ),
+        ),
+    )
+
+
+@contextlib.contextmanager
+def in_env(
+        prefix: Prefix,
+        language_version: str,
+) -> Generator[None, None, None]:
+    with envcontext(get_env_patch(_envdir(prefix, language_version))):
+        yield
+
+
+def install_environment(
+        prefix: Prefix, version: str, additional_dependencies: Sequence[str],
+) -> None:
+    helpers.assert_version_default('perl', version)
+
+    with clean_path_on_failure(_envdir(prefix, version)):
+        with in_env(prefix, version):
+            helpers.run_setup_cmd(
+                prefix, ('cpan', '-T', '.', *additional_dependencies),
+            )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    with in_env(hook.prefix, hook.language_version):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/pygrep.py b/pre_commit/languages/pygrep.py
new file mode 100644
index 0000000..40adba0
--- /dev/null
+++ b/pre_commit/languages/pygrep.py
@@ -0,0 +1,87 @@
+import argparse
+import re
+import sys
+from typing import Optional
+from typing import Pattern
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit import output
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.xargs import xargs
+
+ENVIRONMENT_DIR = None
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+install_environment = helpers.no_install
+
+
+def _process_filename_by_line(pattern: Pattern[bytes], filename: str) -> int:
+    retv = 0
+    with open(filename, 'rb') as f:
+        for line_no, line in enumerate(f, start=1):
+            if pattern.search(line):
+                retv = 1
+                output.write(f'{filename}:{line_no}:')
+                output.write_line_b(line.rstrip(b'\r\n'))
+    return retv
+
+
+def _process_filename_at_once(pattern: Pattern[bytes], filename: str) -> int:
+    retv = 0
+    with open(filename, 'rb') as f:
+        contents = f.read()
+        match = pattern.search(contents)
+        if match:
+            retv = 1
+            line_no = contents[:match.start()].count(b'\n')
+            output.write(f'{filename}:{line_no + 1}:')
+
+            matched_lines = match[0].split(b'\n')
+            matched_lines[0] = contents.split(b'\n')[line_no]
+
+            output.write_line_b(b'\n'.join(matched_lines))
+    return retv
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    exe = (sys.executable, '-m', __name__) + tuple(hook.args) + (hook.entry,)
+    return xargs(exe, file_args, color=color)
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser(
+        description=(
+            'grep-like finder using python regexes.  Unlike grep, this tool '
+            'returns nonzero when it finds a match and zero otherwise.  The '
+            'idea here being that matches are "problems".'
+        ),
+    )
+    parser.add_argument('-i', '--ignore-case', action='store_true')
+    parser.add_argument('--multiline', action='store_true')
+    parser.add_argument('pattern', help='python regex pattern.')
+    parser.add_argument('filenames', nargs='*')
+    args = parser.parse_args(argv)
+
+    flags = re.IGNORECASE if args.ignore_case else 0
+    if args.multiline:
+        flags |= re.MULTILINE | re.DOTALL
+
+    pattern = re.compile(args.pattern.encode(), flags)
+
+    retv = 0
+    for filename in args.filenames:
+        if args.multiline:
+            retv |= _process_filename_at_once(pattern, filename)
+        else:
+            retv |= _process_filename_by_line(pattern, filename)
+    return retv
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
new file mode 100644
index 0000000..5073a8b
--- /dev/null
+++ b/pre_commit/languages/python.py
@@ -0,0 +1,210 @@
+import contextlib
+import functools
+import os
+import sys
+from typing import Callable
+from typing import ContextManager
+from typing import Generator
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import UNSET
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.parse_shebang import find_executable
+from pre_commit.prefix import Prefix
+from pre_commit.util import CalledProcessError
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'py_env'
+
+
+def bin_dir(venv: str) -> str:
+    """On windows there's a different directory for the virtualenv"""
+    bin_part = 'Scripts' if os.name == 'nt' else 'bin'
+    return os.path.join(venv, bin_part)
+
+
+def get_env_patch(venv: str) -> PatchesT:
+    return (
+        ('PYTHONHOME', UNSET),
+        ('VIRTUAL_ENV', venv),
+        ('PATH', (bin_dir(venv), os.pathsep, Var('PATH'))),
+    )
+
+
+def _find_by_py_launcher(
+        version: str,
+) -> Optional[str]:  # pragma: no cover (windows only)
+    if version.startswith('python'):
+        num = version[len('python'):]
+        try:
+            cmd = ('py', f'-{num}', '-c', 'import sys; print(sys.executable)')
+            return cmd_output(*cmd)[1].strip()
+        except CalledProcessError:
+            pass
+    return None
+
+
+def _find_by_sys_executable() -> Optional[str]:
+    def _norm(path: str) -> Optional[str]:
+        _, exe = os.path.split(path.lower())
+        exe, _, _ = exe.partition('.exe')
+        if exe not in {'python', 'pythonw'} and find_executable(exe):
+            return exe
+        return None
+
+    # On linux, I see these common sys.executables:
+    #
+    # system `python`: /usr/bin/python -> python2.7
+    # system `python2`: /usr/bin/python2 -> python2.7
+    # virtualenv v: v/bin/python (will not return from this loop)
+    # virtualenv v -ppython2: v/bin/python -> python2
+    # virtualenv v -ppython2.7: v/bin/python -> python2.7
+    # virtualenv v -ppypy: v/bin/python -> v/bin/pypy
+    for path in (sys.executable, os.path.realpath(sys.executable)):
+        exe = _norm(path)
+        if exe:
+            return exe
+    return None
+
+
+@functools.lru_cache(maxsize=1)
+def get_default_version() -> str:  # pragma: no cover (platform dependent)
+    # First attempt from `sys.executable` (or the realpath)
+    exe = _find_by_sys_executable()
+    if exe:
+        return exe
+
+    # Next try the `pythonX.X` executable
+    exe = f'python{sys.version_info[0]}.{sys.version_info[1]}'
+    if find_executable(exe):
+        return exe
+
+    if _find_by_py_launcher(exe):
+        return exe
+
+    # Give a best-effort try for windows
+    default_folder_name = exe.replace('.', '')
+    if os.path.exists(fr'C:\{default_folder_name}\python.exe'):
+        return exe
+
+    # We tried!
+    return C.DEFAULT
+
+
+def _sys_executable_matches(version: str) -> bool:
+    if version == 'python':
+        return True
+    elif not version.startswith('python'):
+        return False
+
+    try:
+        info = tuple(int(p) for p in version[len('python'):].split('.'))
+    except ValueError:
+        return False
+
+    return sys.version_info[:len(info)] == info
+
+
+def norm_version(version: str) -> str:
+    # first see if our current executable is appropriate
+    if _sys_executable_matches(version):
+        return sys.executable
+
+    if os.name == 'nt':  # pragma: no cover (windows)
+        version_exec = _find_by_py_launcher(version)
+        if version_exec:
+            return version_exec
+
+        # Try looking up by name
+        version_exec = find_executable(version)
+        if version_exec and version_exec != version:
+            return version_exec
+
+        # If it is in the form pythonx.x search in the default
+        # place on windows
+        if version.startswith('python'):
+            default_folder_name = version.replace('.', '')
+            return fr'C:\{default_folder_name}\python.exe'
+
+    # Otherwise assume it is a path
+    return os.path.expanduser(version)
+
+
+def py_interface(
+        _dir: str,
+        _make_venv: Callable[[str, str], None],
+) -> Tuple[
+    Callable[[Prefix, str], ContextManager[None]],
+    Callable[[Prefix, str], bool],
+    Callable[[Hook, Sequence[str], bool], Tuple[int, bytes]],
+    Callable[[Prefix, str, Sequence[str]], None],
+]:
+    @contextlib.contextmanager
+    def in_env(
+            prefix: Prefix,
+            language_version: str,
+    ) -> Generator[None, None, None]:
+        envdir = prefix.path(helpers.environment_dir(_dir, language_version))
+        with envcontext(get_env_patch(envdir)):
+            yield
+
+    def healthy(prefix: Prefix, language_version: str) -> bool:
+        envdir = helpers.environment_dir(_dir, language_version)
+        exe_name = 'python.exe' if sys.platform == 'win32' else 'python'
+        py_exe = prefix.path(bin_dir(envdir), exe_name)
+        with in_env(prefix, language_version):
+            retcode, _, _ = cmd_output_b(
+                py_exe, '-c', 'import ctypes, datetime, io, os, ssl, weakref',
+                cwd='/',
+                retcode=None,
+            )
+        return retcode == 0
+
+    def run_hook(
+            hook: Hook,
+            file_args: Sequence[str],
+            color: bool,
+    ) -> Tuple[int, bytes]:
+        with in_env(hook.prefix, hook.language_version):
+            return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
+
+    def install_environment(
+            prefix: Prefix,
+            version: str,
+            additional_dependencies: Sequence[str],
+    ) -> None:
+        additional_dependencies = tuple(additional_dependencies)
+        directory = helpers.environment_dir(_dir, version)
+
+        env_dir = prefix.path(directory)
+        with clean_path_on_failure(env_dir):
+            if version != C.DEFAULT:
+                python = norm_version(version)
+            else:
+                python = os.path.realpath(sys.executable)
+            _make_venv(env_dir, python)
+            with in_env(prefix, version):
+                helpers.run_setup_cmd(
+                    prefix, ('pip', 'install', '.') + additional_dependencies,
+                )
+
+    return in_env, healthy, run_hook, install_environment
+
+
+def make_venv(envdir: str, python: str) -> None:
+    env = dict(os.environ, VIRTUALENV_NO_DOWNLOAD='1')
+    cmd = (sys.executable, '-mvirtualenv', envdir, '-p', python)
+    cmd_output_b(*cmd, env=env, cwd='/')
+
+
+_interface = py_interface(ENVIRONMENT_DIR, make_venv)
+in_env, healthy, run_hook, install_environment = _interface
diff --git a/pre_commit/languages/python_venv.py b/pre_commit/languages/python_venv.py
new file mode 100644
index 0000000..5404c8b
--- /dev/null
+++ b/pre_commit/languages/python_venv.py
@@ -0,0 +1,46 @@
+import os.path
+
+from pre_commit.languages import python
+from pre_commit.util import CalledProcessError
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'py_venv'
+get_default_version = python.get_default_version
+
+
+def orig_py_exe(exe: str) -> str:  # pragma: no cover (platform specific)
+    """A -mvenv virtualenv made from a -mvirtualenv virtualenv installs
+    packages to the incorrect location.  Attempt to find the _original_ exe
+    and invoke `-mvenv` from there.
+
+    See:
+    - https://github.com/pre-commit/pre-commit/issues/755
+    - https://github.com/pypa/virtualenv/issues/1095
+    - https://bugs.python.org/issue30811
+    """
+    try:
+        prefix_script = 'import sys; print(sys.real_prefix)'
+        _, prefix, _ = cmd_output(exe, '-c', prefix_script)
+        prefix = prefix.strip()
+    except CalledProcessError:
+        # not created from -mvirtualenv
+        return exe
+
+    if os.name == 'nt':
+        expected = os.path.join(prefix, 'python.exe')
+    else:
+        expected = os.path.join(prefix, 'bin', os.path.basename(exe))
+
+    if os.path.exists(expected):
+        return expected
+    else:
+        return exe
+
+
+def make_venv(envdir: str, python: str) -> None:
+    cmd_output_b(orig_py_exe(python), '-mvenv', envdir, cwd='/')
+
+
+_interface = python.py_interface(ENVIRONMENT_DIR, make_venv)
+in_env, healthy, run_hook, install_environment = _interface
diff --git a/pre_commit/languages/ruby.py b/pre_commit/languages/ruby.py
new file mode 100644
index 0000000..61241f8
--- /dev/null
+++ b/pre_commit/languages/ruby.py
@@ -0,0 +1,126 @@
+import contextlib
+import os.path
+import shutil
+import tarfile
+from typing import Generator
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import CalledProcessError
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import resource_bytesio
+
+ENVIRONMENT_DIR = 'rbenv'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def get_env_patch(
+        venv: str,
+        language_version: str,
+) -> PatchesT:  # pragma: win32 no cover
+    patches: PatchesT = (
+        ('GEM_HOME', os.path.join(venv, 'gems')),
+        ('RBENV_ROOT', venv),
+        ('BUNDLE_IGNORE_CONFIG', '1'),
+        (
+            'PATH', (
+                os.path.join(venv, 'gems', 'bin'), os.pathsep,
+                os.path.join(venv, 'shims'), os.pathsep,
+                os.path.join(venv, 'bin'), os.pathsep, Var('PATH'),
+            ),
+        ),
+    )
+    if language_version != C.DEFAULT:
+        patches += (('RBENV_VERSION', language_version),)
+    return patches
+
+
+@contextlib.contextmanager  # pragma: win32 no cover
+def in_env(
+        prefix: Prefix,
+        language_version: str,
+) -> Generator[None, None, None]:
+    envdir = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, language_version),
+    )
+    with envcontext(get_env_patch(envdir, language_version)):
+        yield
+
+
+def _extract_resource(filename: str, dest: str) -> None:
+    with resource_bytesio(filename) as bio:
+        with tarfile.open(fileobj=bio) as tf:
+            tf.extractall(dest)
+
+
+def _install_rbenv(
+        prefix: Prefix,
+        version: str = C.DEFAULT,
+) -> None:  # pragma: win32 no cover
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
+
+    _extract_resource('rbenv.tar.gz', prefix.path('.'))
+    shutil.move(prefix.path('rbenv'), prefix.path(directory))
+
+    # Only install ruby-build if the version is specified
+    if version != C.DEFAULT:
+        plugins_dir = prefix.path(directory, 'plugins')
+        _extract_resource('ruby-download.tar.gz', plugins_dir)
+        _extract_resource('ruby-build.tar.gz', plugins_dir)
+
+
+def _install_ruby(
+        prefix: Prefix,
+        version: str,
+) -> None:  # pragma: win32 no cover
+    try:
+        helpers.run_setup_cmd(prefix, ('rbenv', 'download', version))
+    except CalledProcessError:  # pragma: no cover (usually find with download)
+        # Failed to download from mirror for some reason, build it instead
+        helpers.run_setup_cmd(prefix, ('rbenv', 'install', version))
+
+
+def install_environment(
+        prefix: Prefix, version: str, additional_dependencies: Sequence[str],
+) -> None:  # pragma: win32 no cover
+    additional_dependencies = tuple(additional_dependencies)
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
+    with clean_path_on_failure(prefix.path(directory)):
+        # TODO: this currently will fail if there's no version specified and
+        # there's no system ruby installed.  Is this ok?
+        _install_rbenv(prefix, version=version)
+        with in_env(prefix, version):
+            # Need to call this before installing so rbenv's directories are
+            # set up
+            helpers.run_setup_cmd(prefix, ('rbenv', 'init', '-'))
+            if version != C.DEFAULT:
+                _install_ruby(prefix, version)
+            # Need to call this after installing to set up the shims
+            helpers.run_setup_cmd(prefix, ('rbenv', 'rehash'))
+            helpers.run_setup_cmd(
+                prefix, ('gem', 'build', *prefix.star('.gemspec')),
+            )
+            helpers.run_setup_cmd(
+                prefix,
+                (
+                    'gem', 'install', '--no-document',
+                    *prefix.star('.gem'), *additional_dependencies,
+                ),
+            )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:  # pragma: win32 no cover
+    with in_env(hook.prefix, hook.language_version):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/rust.py b/pre_commit/languages/rust.py
new file mode 100644
index 0000000..7ea3f54
--- /dev/null
+++ b/pre_commit/languages/rust.py
@@ -0,0 +1,106 @@
+import contextlib
+import os.path
+from typing import Generator
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+
+import toml
+
+import pre_commit.constants as C
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'rustenv'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def get_env_patch(target_dir: str) -> PatchesT:
+    return (
+        ('PATH', (os.path.join(target_dir, 'bin'), os.pathsep, Var('PATH'))),
+    )
+
+
+@contextlib.contextmanager
+def in_env(prefix: Prefix) -> Generator[None, None, None]:
+    target_dir = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+    with envcontext(get_env_patch(target_dir)):
+        yield
+
+
+def _add_dependencies(
+        cargo_toml_path: str,
+        additional_dependencies: Set[str],
+) -> None:
+    with open(cargo_toml_path, 'r+') as f:
+        cargo_toml = toml.load(f)
+        cargo_toml.setdefault('dependencies', {})
+        for dep in additional_dependencies:
+            name, _, spec = dep.partition(':')
+            cargo_toml['dependencies'][name] = spec or '*'
+        f.seek(0)
+        toml.dump(cargo_toml, f)
+        f.truncate()
+
+
+def install_environment(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> None:
+    helpers.assert_version_default('rust', version)
+    directory = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+
+    # There are two cases where we might want to specify more dependencies:
+    # as dependencies for the library being built, and as binary packages
+    # to be `cargo install`'d.
+    #
+    # Unlike e.g. Python, if we just `cargo install` a library, it won't be
+    # used for compilation. And if we add a crate providing a binary to the
+    # `Cargo.toml`, the binary won't be built.
+    #
+    # Because of this, we allow specifying "cli" dependencies by prefixing
+    # with 'cli:'.
+    cli_deps = {
+        dep for dep in additional_dependencies if dep.startswith('cli:')
+    }
+    lib_deps = set(additional_dependencies) - cli_deps
+
+    if len(lib_deps) > 0:
+        _add_dependencies(prefix.path('Cargo.toml'), lib_deps)
+
+    with clean_path_on_failure(directory):
+        packages_to_install: Set[Tuple[str, ...]] = {('--path', '.')}
+        for cli_dep in cli_deps:
+            cli_dep = cli_dep[len('cli:'):]
+            package, _, version = cli_dep.partition(':')
+            if version != '':
+                packages_to_install.add((package, '--version', version))
+            else:
+                packages_to_install.add((package,))
+
+        for args in packages_to_install:
+            cmd_output_b(
+                'cargo', 'install', '--bins', '--root', directory, *args,
+                cwd=prefix.prefix_dir,
+            )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    with in_env(hook.prefix):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/script.py b/pre_commit/languages/script.py
new file mode 100644
index 0000000..a5e1365
--- /dev/null
+++ b/pre_commit/languages/script.py
@@ -0,0 +1,19 @@
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+
+ENVIRONMENT_DIR = None
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+install_environment = helpers.no_install
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    cmd = (hook.prefix.path(hook.cmd[0]), *hook.cmd[1:])
+    return helpers.run_xargs(hook, cmd, file_args, color=color)
diff --git a/pre_commit/languages/swift.py b/pre_commit/languages/swift.py
new file mode 100644
index 0000000..66aadc8
--- /dev/null
+++ b/pre_commit/languages/swift.py
@@ -0,0 +1,64 @@
+import contextlib
+import os
+from typing import Generator
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import Var
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'swift_env'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+BUILD_DIR = '.build'
+BUILD_CONFIG = 'release'
+
+
+def get_env_patch(venv: str) -> PatchesT:  # pragma: win32 no cover
+    bin_path = os.path.join(venv, BUILD_DIR, BUILD_CONFIG)
+    return (('PATH', (bin_path, os.pathsep, Var('PATH'))),)
+
+
+@contextlib.contextmanager  # pragma: win32 no cover
+def in_env(prefix: Prefix) -> Generator[None, None, None]:
+    envdir = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+    with envcontext(get_env_patch(envdir)):
+        yield
+
+
+def install_environment(
+        prefix: Prefix, version: str, additional_dependencies: Sequence[str],
+) -> None:  # pragma: win32 no cover
+    helpers.assert_version_default('swift', version)
+    helpers.assert_no_additional_deps('swift', additional_dependencies)
+    directory = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+
+    # Build the swift package
+    with clean_path_on_failure(directory):
+        os.mkdir(directory)
+        cmd_output_b(
+            'swift', 'build',
+            '-C', prefix.prefix_dir,
+            '-c', BUILD_CONFIG,
+            '--build-path', os.path.join(directory, BUILD_DIR),
+        )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:  # pragma: win32 no cover
+    with in_env(hook.prefix):
+        return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/languages/system.py b/pre_commit/languages/system.py
new file mode 100644
index 0000000..139f45d
--- /dev/null
+++ b/pre_commit/languages/system.py
@@ -0,0 +1,19 @@
+from typing import Sequence
+from typing import Tuple
+
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+
+
+ENVIRONMENT_DIR = None
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+install_environment = helpers.no_install
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:
+    return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
diff --git a/pre_commit/logging_handler.py b/pre_commit/logging_handler.py
new file mode 100644
index 0000000..ba05295
--- /dev/null
+++ b/pre_commit/logging_handler.py
@@ -0,0 +1,40 @@
+import contextlib
+import logging
+from typing import Generator
+
+from pre_commit import color
+from pre_commit import output
+
+logger = logging.getLogger('pre_commit')
+
+LOG_LEVEL_COLORS = {
+    'DEBUG': '',
+    'INFO': '',
+    'WARNING': color.YELLOW,
+    'ERROR': color.RED,
+}
+
+
+class LoggingHandler(logging.Handler):
+    def __init__(self, use_color: bool) -> None:
+        super().__init__()
+        self.use_color = use_color
+
+    def emit(self, record: logging.LogRecord) -> None:
+        level_msg = color.format_color(
+            f'[{record.levelname}]',
+            LOG_LEVEL_COLORS[record.levelname],
+            self.use_color,
+        )
+        output.write_line(f'{level_msg} {record.getMessage()}')
+
+
+@contextlib.contextmanager
+def logging_handler(use_color: bool) -> Generator[None, None, None]:
+    handler = LoggingHandler(use_color)
+    logger.addHandler(handler)
+    logger.setLevel(logging.INFO)
+    try:
+        yield
+    finally:
+        logger.removeHandler(handler)
diff --git a/pre_commit/main.py b/pre_commit/main.py
new file mode 100644
index 0000000..790b347
--- /dev/null
+++ b/pre_commit/main.py
@@ -0,0 +1,410 @@
+import argparse
+import logging
+import os
+import sys
+from typing import Any
+from typing import Optional
+from typing import Sequence
+from typing import Union
+
+import pre_commit.constants as C
+from pre_commit import color
+from pre_commit import git
+from pre_commit.commands.autoupdate import autoupdate
+from pre_commit.commands.clean import clean
+from pre_commit.commands.gc import gc
+from pre_commit.commands.hook_impl import hook_impl
+from pre_commit.commands.init_templatedir import init_templatedir
+from pre_commit.commands.install_uninstall import install
+from pre_commit.commands.install_uninstall import install_hooks
+from pre_commit.commands.install_uninstall import uninstall
+from pre_commit.commands.migrate_config import migrate_config
+from pre_commit.commands.run import run
+from pre_commit.commands.sample_config import sample_config
+from pre_commit.commands.try_repo import try_repo
+from pre_commit.error_handler import error_handler
+from pre_commit.error_handler import FatalError
+from pre_commit.logging_handler import logging_handler
+from pre_commit.store import Store
+from pre_commit.util import CalledProcessError
+
+
+logger = logging.getLogger('pre_commit')
+
+# https://github.com/pre-commit/pre-commit/issues/217
+# On OSX, making a virtualenv using pyvenv at . causes `virtualenv` and `pip`
+# to install packages to the wrong place.  We don't want anything to deal with
+# pyvenv
+os.environ.pop('__PYVENV_LAUNCHER__', None)
+
+
+COMMANDS_NO_GIT = {'clean', 'gc', 'init-templatedir', 'sample-config'}
+
+
+def _add_color_option(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        '--color', default=os.environ.get('PRE_COMMIT_COLOR', 'auto'),
+        type=color.use_color,
+        metavar='{' + ','.join(color.COLOR_CHOICES) + '}',
+        help='Whether to use color in output.  Defaults to `%(default)s`.',
+    )
+
+
+def _add_config_option(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        '-c', '--config', default=C.CONFIG_FILE,
+        help='Path to alternate config file',
+    )
+
+
+class AppendReplaceDefault(argparse.Action):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
+        self.appended = False
+
+    def __call__(
+            self,
+            parser: argparse.ArgumentParser,
+            namespace: argparse.Namespace,
+            values: Union[str, Sequence[str], None],
+            option_string: Optional[str] = None,
+    ) -> None:
+        if not self.appended:
+            setattr(namespace, self.dest, [])
+            self.appended = True
+        getattr(namespace, self.dest).append(values)
+
+
+def _add_hook_type_option(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        '-t', '--hook-type', choices=(
+            'pre-commit', 'pre-merge-commit', 'pre-push',
+            'prepare-commit-msg', 'commit-msg', 'post-checkout',
+        ),
+        action=AppendReplaceDefault,
+        default=['pre-commit'],
+        dest='hook_types',
+    )
+
+
+def _add_run_options(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument('hook', nargs='?', help='A single hook-id to run')
+    parser.add_argument('--verbose', '-v', action='store_true', default=False)
+    mutex_group = parser.add_mutually_exclusive_group(required=False)
+    mutex_group.add_argument(
+        '--all-files', '-a', action='store_true', default=False,
+        help='Run on all the files in the repo.',
+    )
+    mutex_group.add_argument(
+        '--files', nargs='*', default=[],
+        help='Specific filenames to run hooks on.',
+    )
+    parser.add_argument(
+        '--show-diff-on-failure', action='store_true',
+        help='When hooks fail, run `git diff` directly afterward.',
+    )
+    parser.add_argument(
+        '--hook-stage', choices=C.STAGES, default='commit',
+        help='The stage during which the hook is fired.  One of %(choices)s',
+    )
+    parser.add_argument(
+        '--from-ref', '--source', '-s',
+        help=(
+            '(for usage with `--from-ref`) -- this option represents the '
+            'original ref in a `from_ref...to_ref` diff expression.  '
+            'For `pre-push` hooks, this represents the branch you are pushing '
+            'to.  '
+            'For `post-checkout` hooks, this represents the branch that was '
+            'previously checked out.'
+        ),
+    )
+    parser.add_argument(
+        '--to-ref', '--origin', '-o',
+        help=(
+            '(for usage with `--to-ref`) -- this option represents the '
+            'destination ref in a `from_ref...to_ref` diff expression.  '
+            'For `pre-push` hooks, this represents the branch being pushed.  '
+            'For `post-checkout` hooks, this represents the branch that is '
+            'now checked out.'
+        ),
+    )
+    parser.add_argument(
+        '--commit-msg-filename',
+        help='Filename to check when running during `commit-msg`',
+    )
+    parser.add_argument(
+        '--remote-name', help='Remote name used by `git push`.',
+    )
+    parser.add_argument('--remote-url', help='Remote url used by `git push`.')
+    parser.add_argument(
+        '--checkout-type',
+        help=(
+            'Indicates whether the checkout was a branch checkout '
+            '(changing branches, flag=1) or a file checkout (retrieving a '
+            'file from the index, flag=0).'
+        ),
+    )
+
+
+def _adjust_args_and_chdir(args: argparse.Namespace) -> None:
+    # `--config` was specified relative to the non-root working directory
+    if os.path.exists(args.config):
+        args.config = os.path.abspath(args.config)
+    if args.command in {'run', 'try-repo'}:
+        args.files = [os.path.abspath(filename) for filename in args.files]
+    if args.command == 'try-repo' and os.path.exists(args.repo):
+        args.repo = os.path.abspath(args.repo)
+
+    try:
+        toplevel = git.get_root()
+    except CalledProcessError:
+        raise FatalError(
+            'git failed. Is it installed, and are you in a Git repository '
+            'directory?',
+        )
+    else:
+        if toplevel == '':  # pragma: no cover (old git)
+            raise FatalError(
+                'git toplevel unexpectedly empty! make sure you are not '
+                'inside the `.git` directory of your repository.',
+            )
+        else:
+            os.chdir(toplevel)
+
+    args.config = os.path.relpath(args.config)
+    if args.command in {'run', 'try-repo'}:
+        args.files = [os.path.relpath(filename) for filename in args.files]
+    if args.command == 'try-repo' and os.path.exists(args.repo):
+        args.repo = os.path.relpath(args.repo)
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    argv = argv if argv is not None else sys.argv[1:]
+    parser = argparse.ArgumentParser(prog='pre-commit')
+
+    # https://stackoverflow.com/a/8521644/812183
+    parser.add_argument(
+        '-V', '--version',
+        action='version',
+        version=f'%(prog)s {C.VERSION}',
+    )
+
+    subparsers = parser.add_subparsers(dest='command')
+
+    autoupdate_parser = subparsers.add_parser(
+        'autoupdate',
+        help="Auto-update pre-commit config to the latest repos' versions.",
+    )
+    _add_color_option(autoupdate_parser)
+    _add_config_option(autoupdate_parser)
+    autoupdate_parser.add_argument(
+        '--bleeding-edge', action='store_true',
+        help=(
+            'Update to the bleeding edge of `master` instead of the latest '
+            'tagged version (the default behavior).'
+        ),
+    )
+    autoupdate_parser.add_argument(
+        '--freeze', action='store_true',
+        help='Store "frozen" hashes in `rev` instead of tag names',
+    )
+    autoupdate_parser.add_argument(
+        '--repo', dest='repos', action='append', metavar='REPO',
+        help='Only update this repository -- may be specified multiple times.',
+    )
+
+    clean_parser = subparsers.add_parser(
+        'clean', help='Clean out pre-commit files.',
+    )
+    _add_color_option(clean_parser)
+    _add_config_option(clean_parser)
+
+    hook_impl_parser = subparsers.add_parser('hook-impl')
+    _add_color_option(hook_impl_parser)
+    _add_config_option(hook_impl_parser)
+    hook_impl_parser.add_argument('--hook-type')
+    hook_impl_parser.add_argument('--hook-dir')
+    hook_impl_parser.add_argument(
+        '--skip-on-missing-config', action='store_true',
+    )
+    hook_impl_parser.add_argument(dest='rest', nargs=argparse.REMAINDER)
+
+    gc_parser = subparsers.add_parser('gc', help='Clean unused cached repos.')
+    _add_color_option(gc_parser)
+    _add_config_option(gc_parser)
+
+    init_templatedir_parser = subparsers.add_parser(
+        'init-templatedir',
+        help=(
+            'Install hook script in a directory intended for use with '
+            '`git config init.templateDir`.'
+        ),
+    )
+    _add_color_option(init_templatedir_parser)
+    _add_config_option(init_templatedir_parser)
+    init_templatedir_parser.add_argument(
+        'directory', help='The directory in which to write the hook script.',
+    )
+    _add_hook_type_option(init_templatedir_parser)
+
+    install_parser = subparsers.add_parser(
+        'install', help='Install the pre-commit script.',
+    )
+    _add_color_option(install_parser)
+    _add_config_option(install_parser)
+    install_parser.add_argument(
+        '-f', '--overwrite', action='store_true',
+        help='Overwrite existing hooks / remove migration mode.',
+    )
+    install_parser.add_argument(
+        '--install-hooks', action='store_true',
+        help=(
+            'Whether to install hook environments for all environments '
+            'in the config file.'
+        ),
+    )
+    _add_hook_type_option(install_parser)
+    install_parser.add_argument(
+        '--allow-missing-config', action='store_true', default=False,
+        help=(
+            'Whether to allow a missing `pre-commit` configuration file '
+            'or exit with a failure code.'
+        ),
+    )
+
+    install_hooks_parser = subparsers.add_parser(
+        'install-hooks',
+        help=(
+            'Install hook environments for all environments in the config '
+            'file.  You may find `pre-commit install --install-hooks` more '
+            'useful.'
+        ),
+    )
+    _add_color_option(install_hooks_parser)
+    _add_config_option(install_hooks_parser)
+
+    migrate_config_parser = subparsers.add_parser(
+        'migrate-config',
+        help='Migrate list configuration to new map configuration.',
+    )
+    _add_color_option(migrate_config_parser)
+    _add_config_option(migrate_config_parser)
+
+    run_parser = subparsers.add_parser('run', help='Run hooks.')
+    _add_color_option(run_parser)
+    _add_config_option(run_parser)
+    _add_run_options(run_parser)
+
+    sample_config_parser = subparsers.add_parser(
+        'sample-config', help=f'Produce a sample {C.CONFIG_FILE} file',
+    )
+    _add_color_option(sample_config_parser)
+    _add_config_option(sample_config_parser)
+
+    try_repo_parser = subparsers.add_parser(
+        'try-repo',
+        help='Try the hooks in a repository, useful for developing new hooks.',
+    )
+    _add_color_option(try_repo_parser)
+    _add_config_option(try_repo_parser)
+    try_repo_parser.add_argument(
+        'repo', help='Repository to source hooks from.',
+    )
+    try_repo_parser.add_argument(
+        '--ref', '--rev',
+        help=(
+            'Manually select a rev to run against, otherwise the `HEAD` '
+            'revision will be used.'
+        ),
+    )
+    _add_run_options(try_repo_parser)
+
+    uninstall_parser = subparsers.add_parser(
+        'uninstall', help='Uninstall the pre-commit script.',
+    )
+    _add_color_option(uninstall_parser)
+    _add_config_option(uninstall_parser)
+    _add_hook_type_option(uninstall_parser)
+
+    help = subparsers.add_parser(
+        'help', help='Show help for a specific command.',
+    )
+    help.add_argument('help_cmd', nargs='?', help='Command to show help for.')
+
+    # argparse doesn't really provide a way to use a `default` subparser
+    if len(argv) == 0:
+        argv = ['run']
+    args = parser.parse_args(argv)
+
+    if args.command == 'help' and args.help_cmd:
+        parser.parse_args([args.help_cmd, '--help'])
+    elif args.command == 'help':
+        parser.parse_args(['--help'])
+
+    with error_handler(), logging_handler(args.color):
+        if args.command not in COMMANDS_NO_GIT:
+            _adjust_args_and_chdir(args)
+
+        git.check_for_cygwin_mismatch()
+
+        store = Store()
+        store.mark_config_used(args.config)
+
+        if args.command == 'autoupdate':
+            return autoupdate(
+                args.config, store,
+                tags_only=not args.bleeding_edge,
+                freeze=args.freeze,
+                repos=args.repos,
+            )
+        elif args.command == 'clean':
+            return clean(store)
+        elif args.command == 'gc':
+            return gc(store)
+        elif args.command == 'hook-impl':
+            return hook_impl(
+                store,
+                config=args.config,
+                color=args.color,
+                hook_type=args.hook_type,
+                hook_dir=args.hook_dir,
+                skip_on_missing_config=args.skip_on_missing_config,
+                args=args.rest[1:],
+            )
+        elif args.command == 'install':
+            return install(
+                args.config, store,
+                hook_types=args.hook_types,
+                overwrite=args.overwrite,
+                hooks=args.install_hooks,
+                skip_on_missing_config=args.allow_missing_config,
+            )
+        elif args.command == 'init-templatedir':
+            return init_templatedir(
+                args.config, store, args.directory,
+                hook_types=args.hook_types,
+            )
+        elif args.command == 'install-hooks':
+            return install_hooks(args.config, store)
+        elif args.command == 'migrate-config':
+            return migrate_config(args.config)
+        elif args.command == 'run':
+            return run(args.config, store, args)
+        elif args.command == 'sample-config':
+            return sample_config()
+        elif args.command == 'try-repo':
+            return try_repo(args)
+        elif args.command == 'uninstall':
+            return uninstall(hook_types=args.hook_types)
+        else:
+            raise NotImplementedError(
+                f'Command {args.command} not implemented.',
+            )
+
+        raise AssertionError(
+            f'Command {args.command} failed to exit with a returncode',
+        )
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/make_archives.py b/pre_commit/make_archives.py
new file mode 100644
index 0000000..c31bcd7
--- /dev/null
+++ b/pre_commit/make_archives.py
@@ -0,0 +1,65 @@
+import argparse
+import os.path
+import tarfile
+from typing import Optional
+from typing import Sequence
+
+from pre_commit import output
+from pre_commit.util import cmd_output_b
+from pre_commit.util import rmtree
+from pre_commit.util import tmpdir
+
+
+# This is a script for generating the tarred resources for git repo
+# dependencies.  Currently it's just for "vendoring" ruby support packages.
+
+
+REPOS = (
+    ('rbenv', 'git://github.com/rbenv/rbenv', 'a3fa9b7'),
+    ('ruby-build', 'git://github.com/rbenv/ruby-build', '1a902f3'),
+    (
+        'ruby-download',
+        'git://github.com/garnieretienne/rvm-download',
+        '09bd7c6',
+    ),
+)
+
+
+def make_archive(name: str, repo: str, ref: str, destdir: str) -> str:
+    """Makes an archive of a repository in the given destdir.
+
+    :param text name: Name to give the archive.  For instance foo.  The file
+    that is created will be called foo.tar.gz.
+    :param text repo: Repository to clone.
+    :param text ref: Tag/SHA/branch to check out.
+    :param text destdir: Directory to place archives in.
+    """
+    output_path = os.path.join(destdir, f'{name}.tar.gz')
+    with tmpdir() as tempdir:
+        # Clone the repository to the temporary directory
+        cmd_output_b('git', 'clone', repo, tempdir)
+        cmd_output_b('git', 'checkout', ref, cwd=tempdir)
+
+        # We don't want the '.git' directory
+        # It adds a bunch of size to the archive and we don't use it at
+        # runtime
+        rmtree(os.path.join(tempdir, '.git'))
+
+        with tarfile.open(output_path, 'w|gz') as tf:
+            tf.add(tempdir, name)
+
+    return output_path
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--dest', default='pre_commit/resources')
+    args = parser.parse_args(argv)
+    for archive_name, repo, ref in REPOS:
+        output.write_line(f'Making {archive_name}.tar.gz for {repo}@{ref}')
+        make_archive(archive_name, repo, ref, args.dest)
+    return 0
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/meta_hooks/__init__.py b/pre_commit/meta_hooks/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/pre_commit/meta_hooks/__init__.py
diff --git a/pre_commit/meta_hooks/check_hooks_apply.py b/pre_commit/meta_hooks/check_hooks_apply.py
new file mode 100644
index 0000000..d0244a9
--- /dev/null
+++ b/pre_commit/meta_hooks/check_hooks_apply.py
@@ -0,0 +1,39 @@
+import argparse
+from typing import Optional
+from typing import Sequence
+
+import pre_commit.constants as C
+from pre_commit import git
+from pre_commit.clientlib import load_config
+from pre_commit.commands.run import Classifier
+from pre_commit.repository import all_hooks
+from pre_commit.store import Store
+
+
+def check_all_hooks_match_files(config_file: str) -> int:
+    classifier = Classifier(git.get_all_files())
+    retv = 0
+
+    for hook in all_hooks(load_config(config_file), Store()):
+        if hook.always_run or hook.language == 'fail':
+            continue
+        elif not classifier.filenames_for_hook(hook):
+            print(f'{hook.id} does not apply to this repository')
+            retv = 1
+
+    return retv
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', default=[C.CONFIG_FILE])
+    args = parser.parse_args(argv)
+
+    retv = 0
+    for filename in args.filenames:
+        retv |= check_all_hooks_match_files(filename)
+    return retv
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/meta_hooks/check_useless_excludes.py b/pre_commit/meta_hooks/check_useless_excludes.py
new file mode 100644
index 0000000..30b8d81
--- /dev/null
+++ b/pre_commit/meta_hooks/check_useless_excludes.py
@@ -0,0 +1,72 @@
+import argparse
+import re
+from typing import Optional
+from typing import Sequence
+
+from cfgv import apply_defaults
+
+import pre_commit.constants as C
+from pre_commit import git
+from pre_commit.clientlib import load_config
+from pre_commit.clientlib import MANIFEST_HOOK_DICT
+from pre_commit.commands.run import Classifier
+
+
+def exclude_matches_any(
+        filenames: Sequence[str],
+        include: str,
+        exclude: str,
+) -> bool:
+    if exclude == '^$':
+        return True
+    include_re, exclude_re = re.compile(include), re.compile(exclude)
+    for filename in filenames:
+        if include_re.search(filename) and exclude_re.search(filename):
+            return True
+    return False
+
+
+def check_useless_excludes(config_file: str) -> int:
+    config = load_config(config_file)
+    classifier = Classifier(git.get_all_files())
+    retv = 0
+
+    exclude = config['exclude']
+    if not exclude_matches_any(classifier.filenames, '', exclude):
+        print(
+            f'The global exclude pattern {exclude!r} does not match any files',
+        )
+        retv = 1
+
+    for repo in config['repos']:
+        for hook in repo['hooks']:
+            # Not actually a manifest dict, but this more accurately reflects
+            # the defaults applied during runtime
+            hook = apply_defaults(hook, MANIFEST_HOOK_DICT)
+            names = classifier.filenames
+            types, exclude_types = hook['types'], hook['exclude_types']
+            names = classifier.by_types(names, types, exclude_types)
+            include, exclude = hook['files'], hook['exclude']
+            if not exclude_matches_any(names, include, exclude):
+                print(
+                    f'The exclude pattern {exclude!r} for {hook["id"]} does '
+                    f'not match any files',
+                )
+                retv = 1
+
+    return retv
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', default=[C.CONFIG_FILE])
+    args = parser.parse_args(argv)
+
+    retv = 0
+    for filename in args.filenames:
+        retv |= check_useless_excludes(filename)
+    return retv
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/meta_hooks/identity.py b/pre_commit/meta_hooks/identity.py
new file mode 100644
index 0000000..730d0ec
--- /dev/null
+++ b/pre_commit/meta_hooks/identity.py
@@ -0,0 +1,16 @@
+import sys
+from typing import Optional
+from typing import Sequence
+
+from pre_commit import output
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    argv = argv if argv is not None else sys.argv[1:]
+    for arg in argv:
+        output.write_line(arg)
+    return 0
+
+
+if __name__ == '__main__':
+    exit(main())
diff --git a/pre_commit/output.py b/pre_commit/output.py
new file mode 100644
index 0000000..24f9d84
--- /dev/null
+++ b/pre_commit/output.py
@@ -0,0 +1,32 @@
+import contextlib
+import sys
+from typing import Any
+from typing import IO
+from typing import Optional
+
+
+def write(s: str, stream: IO[bytes] = sys.stdout.buffer) -> None:
+    stream.write(s.encode())
+    stream.flush()
+
+
+def write_line_b(
+        s: Optional[bytes] = None,
+        stream: IO[bytes] = sys.stdout.buffer,
+        logfile_name: Optional[str] = None,
+) -> None:
+    with contextlib.ExitStack() as exit_stack:
+        output_streams = [stream]
+        if logfile_name:
+            stream = exit_stack.enter_context(open(logfile_name, 'ab'))
+            output_streams.append(stream)
+
+        for output_stream in output_streams:
+            if s is not None:
+                output_stream.write(s)
+            output_stream.write(b'\n')
+            output_stream.flush()
+
+
+def write_line(s: Optional[str] = None, **kwargs: Any) -> None:
+    write_line_b(s.encode() if s is not None else s, **kwargs)
diff --git a/pre_commit/parse_shebang.py b/pre_commit/parse_shebang.py
new file mode 100644
index 0000000..d344a1d
--- /dev/null
+++ b/pre_commit/parse_shebang.py
@@ -0,0 +1,84 @@
+import os.path
+from typing import Mapping
+from typing import Optional
+from typing import Tuple
+from typing import TYPE_CHECKING
+
+from identify.identify import parse_shebang_from_file
+
+if TYPE_CHECKING:
+    from typing import NoReturn
+
+
+class ExecutableNotFoundError(OSError):
+    def to_output(self) -> Tuple[int, bytes, None]:
+        return (1, self.args[0].encode(), None)
+
+
+def parse_filename(filename: str) -> Tuple[str, ...]:
+    if not os.path.exists(filename):
+        return ()
+    else:
+        return parse_shebang_from_file(filename)
+
+
+def find_executable(
+        exe: str, _environ: Optional[Mapping[str, str]] = None,
+) -> Optional[str]:
+    exe = os.path.normpath(exe)
+    if os.sep in exe:
+        return exe
+
+    environ = _environ if _environ is not None else os.environ
+
+    if 'PATHEXT' in environ:
+        exts = environ['PATHEXT'].split(os.pathsep)
+        possible_exe_names = tuple(f'{exe}{ext}' for ext in exts) + (exe,)
+    else:
+        possible_exe_names = (exe,)
+
+    for path in environ.get('PATH', '').split(os.pathsep):
+        for possible_exe_name in possible_exe_names:
+            joined = os.path.join(path, possible_exe_name)
+            if os.path.isfile(joined) and os.access(joined, os.X_OK):
+                return joined
+    else:
+        return None
+
+
+def normexe(orig: str) -> str:
+    def _error(msg: str) -> 'NoReturn':
+        raise ExecutableNotFoundError(f'Executable `{orig}` {msg}')
+
+    if os.sep not in orig and (not os.altsep or os.altsep not in orig):
+        exe = find_executable(orig)
+        if exe is None:
+            _error('not found')
+        return exe
+    elif os.path.isdir(orig):
+        _error('is a directory')
+    elif not os.path.isfile(orig):
+        _error('not found')
+    elif not os.access(orig, os.X_OK):  # pragma: win32 no cover
+        _error('is not executable')
+    else:
+        return orig
+
+
+def normalize_cmd(cmd: Tuple[str, ...]) -> Tuple[str, ...]:
+    """Fixes for the following issues on windows
+    - https://bugs.python.org/issue8557
+    - windows does not parse shebangs
+
+    This function also makes deep-path shebangs work just fine
+    """
+    # Use PATH to determine the executable
+    exe = normexe(cmd[0])
+
+    # Figure out the shebang from the resulting command
+    cmd = parse_filename(exe) + (exe,) + cmd[1:]
+
+    # This could have given us back another bare executable
+    exe = normexe(cmd[0])
+
+    return (exe,) + cmd[1:]
diff --git a/pre_commit/prefix.py b/pre_commit/prefix.py
new file mode 100644
index 0000000..0e3ebbd
--- /dev/null
+++ b/pre_commit/prefix.py
@@ -0,0 +1,17 @@
+import os.path
+from typing import NamedTuple
+from typing import Tuple
+
+
+class Prefix(NamedTuple):
+    prefix_dir: str
+
+    def path(self, *parts: str) -> str:
+        return os.path.normpath(os.path.join(self.prefix_dir, *parts))
+
+    def exists(self, *parts: str) -> bool:
+        return os.path.exists(self.path(*parts))
+
+    def star(self, end: str) -> Tuple[str, ...]:
+        paths = os.listdir(self.prefix_dir)
+        return tuple(path for path in paths if path.endswith(end))
diff --git a/pre_commit/repository.py b/pre_commit/repository.py
new file mode 100644
index 0000000..77734ee
--- /dev/null
+++ b/pre_commit/repository.py
@@ -0,0 +1,208 @@
+import json
+import logging
+import os
+from typing import Any
+from typing import Dict
+from typing import List
+from typing import Optional
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.clientlib import load_manifest
+from pre_commit.clientlib import LOCAL
+from pre_commit.clientlib import META
+from pre_commit.hook import Hook
+from pre_commit.languages.all import languages
+from pre_commit.languages.helpers import environment_dir
+from pre_commit.prefix import Prefix
+from pre_commit.store import Store
+from pre_commit.util import parse_version
+from pre_commit.util import rmtree
+
+
+logger = logging.getLogger('pre_commit')
+
+
+def _state(additional_deps: Sequence[str]) -> object:
+    return {'additional_dependencies': sorted(additional_deps)}
+
+
+def _state_filename(prefix: Prefix, venv: str) -> str:
+    return prefix.path(venv, f'.install_state_v{C.INSTALLED_STATE_VERSION}')
+
+
+def _read_state(prefix: Prefix, venv: str) -> Optional[object]:
+    filename = _state_filename(prefix, venv)
+    if not os.path.exists(filename):
+        return None
+    else:
+        with open(filename) as f:
+            return json.load(f)
+
+
+def _write_state(prefix: Prefix, venv: str, state: object) -> None:
+    state_filename = _state_filename(prefix, venv)
+    staging = f'{state_filename}staging'
+    with open(staging, 'w') as state_file:
+        state_file.write(json.dumps(state))
+    # Move the file into place atomically to indicate we've installed
+    os.rename(staging, state_filename)
+
+
+def _hook_installed(hook: Hook) -> bool:
+    lang = languages[hook.language]
+    venv = environment_dir(lang.ENVIRONMENT_DIR, hook.language_version)
+    return (
+        venv is None or (
+            (
+                _read_state(hook.prefix, venv) ==
+                _state(hook.additional_dependencies)
+            ) and
+            lang.healthy(hook.prefix, hook.language_version)
+        )
+    )
+
+
+def _hook_install(hook: Hook) -> None:
+    logger.info(f'Installing environment for {hook.src}.')
+    logger.info('Once installed this environment will be reused.')
+    logger.info('This may take a few minutes...')
+
+    lang = languages[hook.language]
+    assert lang.ENVIRONMENT_DIR is not None
+    venv = environment_dir(lang.ENVIRONMENT_DIR, hook.language_version)
+
+    # There's potentially incomplete cleanup from previous runs
+    # Clean it up!
+    if hook.prefix.exists(venv):
+        rmtree(hook.prefix.path(venv))
+
+    lang.install_environment(
+        hook.prefix, hook.language_version, hook.additional_dependencies,
+    )
+    # Write our state to indicate we're installed
+    _write_state(hook.prefix, venv, _state(hook.additional_dependencies))
+
+
+def _hook(
+        *hook_dicts: Dict[str, Any],
+        root_config: Dict[str, Any],
+) -> Dict[str, Any]:
+    ret, rest = dict(hook_dicts[0]), hook_dicts[1:]
+    for dct in rest:
+        ret.update(dct)
+
+    version = ret['minimum_pre_commit_version']
+    if parse_version(version) > parse_version(C.VERSION):
+        logger.error(
+            f'The hook `{ret["id"]}` requires pre-commit version {version} '
+            f'but version {C.VERSION} is installed.  '
+            f'Perhaps run `pip install --upgrade pre-commit`.',
+        )
+        exit(1)
+
+    lang = ret['language']
+    if ret['language_version'] == C.DEFAULT:
+        ret['language_version'] = root_config['default_language_version'][lang]
+    if ret['language_version'] == C.DEFAULT:
+        ret['language_version'] = languages[lang].get_default_version()
+
+    if not ret['stages']:
+        ret['stages'] = root_config['default_stages']
+
+    return ret
+
+
+def _non_cloned_repository_hooks(
+        repo_config: Dict[str, Any],
+        store: Store,
+        root_config: Dict[str, Any],
+) -> Tuple[Hook, ...]:
+    def _prefix(language_name: str, deps: Sequence[str]) -> Prefix:
+        language = languages[language_name]
+        # pygrep / script / system / docker_image do not have
+        # environments so they work out of the current directory
+        if language.ENVIRONMENT_DIR is None:
+            return Prefix(os.getcwd())
+        else:
+            return Prefix(store.make_local(deps))
+
+    return tuple(
+        Hook.create(
+            repo_config['repo'],
+            _prefix(hook['language'], hook['additional_dependencies']),
+            _hook(hook, root_config=root_config),
+        )
+        for hook in repo_config['hooks']
+    )
+
+
+def _cloned_repository_hooks(
+        repo_config: Dict[str, Any],
+        store: Store,
+        root_config: Dict[str, Any],
+) -> Tuple[Hook, ...]:
+    repo, rev = repo_config['repo'], repo_config['rev']
+    manifest_path = os.path.join(store.clone(repo, rev), C.MANIFEST_FILE)
+    by_id = {hook['id']: hook for hook in load_manifest(manifest_path)}
+
+    for hook in repo_config['hooks']:
+        if hook['id'] not in by_id:
+            logger.error(
+                f'`{hook["id"]}` is not present in repository {repo}.  '
+                f'Typo? Perhaps it is introduced in a newer version?  '
+                f'Often `pre-commit autoupdate` fixes this.',
+            )
+            exit(1)
+
+    hook_dcts = [
+        _hook(by_id[hook['id']], hook, root_config=root_config)
+        for hook in repo_config['hooks']
+    ]
+    return tuple(
+        Hook.create(
+            repo_config['repo'],
+            Prefix(store.clone(repo, rev, hook['additional_dependencies'])),
+            hook,
+        )
+        for hook in hook_dcts
+    )
+
+
+def _repository_hooks(
+        repo_config: Dict[str, Any],
+        store: Store,
+        root_config: Dict[str, Any],
+) -> Tuple[Hook, ...]:
+    if repo_config['repo'] in {LOCAL, META}:
+        return _non_cloned_repository_hooks(repo_config, store, root_config)
+    else:
+        return _cloned_repository_hooks(repo_config, store, root_config)
+
+
+def install_hook_envs(hooks: Sequence[Hook], store: Store) -> None:
+    def _need_installed() -> List[Hook]:
+        seen: Set[Tuple[Prefix, str, str, Tuple[str, ...]]] = set()
+        ret = []
+        for hook in hooks:
+            if hook.install_key not in seen and not _hook_installed(hook):
+                ret.append(hook)
+            seen.add(hook.install_key)
+        return ret
+
+    if not _need_installed():
+        return
+    with store.exclusive_lock():
+        # Another process may have already completed this work
+        for hook in _need_installed():
+            _hook_install(hook)
+
+
+def all_hooks(root_config: Dict[str, Any], store: Store) -> Tuple[Hook, ...]:
+    return tuple(
+        hook
+        for repo in root_config['repos']
+        for hook in _repository_hooks(repo, store, root_config)
+    )
diff --git a/pre_commit/resources/__init__.py b/pre_commit/resources/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/pre_commit/resources/__init__.py
diff --git a/pre_commit/resources/empty_template_.npmignore b/pre_commit/resources/empty_template_.npmignore
new file mode 100644
index 0000000..72e8ffc
--- /dev/null
+++ b/pre_commit/resources/empty_template_.npmignore
@@ -0,0 +1 @@
+*
diff --git a/pre_commit/resources/empty_template_Cargo.toml b/pre_commit/resources/empty_template_Cargo.toml
new file mode 100644
index 0000000..3dfeffa
--- /dev/null
+++ b/pre_commit/resources/empty_template_Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "__fake_crate"
+version = "0.0.0"
+
+[[bin]]
+name = "__fake_cmd"
+path = "main.rs"
diff --git a/pre_commit/resources/empty_template_Makefile.PL b/pre_commit/resources/empty_template_Makefile.PL
new file mode 100644
index 0000000..ac75fe5
--- /dev/null
+++ b/pre_commit/resources/empty_template_Makefile.PL
@@ -0,0 +1,6 @@
+use ExtUtils::MakeMaker;
+
+WriteMakefile(
+    NAME => "PreCommitDummy",
+    VERSION => "0.0.1",
+);
diff --git a/pre_commit/resources/empty_template_environment.yml b/pre_commit/resources/empty_template_environment.yml
new file mode 100644
index 0000000..0f29f0c
--- /dev/null
+++ b/pre_commit/resources/empty_template_environment.yml
@@ -0,0 +1,9 @@
+channels:
+  - conda-forge
+  - defaults
+dependencies:
+  # This cannot be empty as otherwise no environment will be created.
+  # We're using openssl here as it is available on all system and will
+  # most likely be always installed anyways.
+  # See https://github.com/conda/conda/issues/9487
+  - openssl
diff --git a/pre_commit/resources/empty_template_main.go b/pre_commit/resources/empty_template_main.go
new file mode 100644
index 0000000..38dd16d
--- /dev/null
+++ b/pre_commit/resources/empty_template_main.go
@@ -0,0 +1,3 @@
+package main
+
+func main() {}
diff --git a/pre_commit/resources/empty_template_main.rs b/pre_commit/resources/empty_template_main.rs
new file mode 100644
index 0000000..f328e4d
--- /dev/null
+++ b/pre_commit/resources/empty_template_main.rs
@@ -0,0 +1 @@
+fn main() {}
diff --git a/pre_commit/resources/empty_template_package.json b/pre_commit/resources/empty_template_package.json
new file mode 100644
index 0000000..ac7b725
--- /dev/null
+++ b/pre_commit/resources/empty_template_package.json
@@ -0,0 +1,4 @@
+{
+    "name": "pre_commit_dummy_package",
+    "version": "0.0.0"
+}
diff --git a/pre_commit/resources/empty_template_pre_commit_dummy_package.gemspec b/pre_commit/resources/empty_template_pre_commit_dummy_package.gemspec
new file mode 100644
index 0000000..8bfb40c
--- /dev/null
+++ b/pre_commit/resources/empty_template_pre_commit_dummy_package.gemspec
@@ -0,0 +1,6 @@
+Gem::Specification.new do |s|
+    s.name = 'pre_commit_dummy_package'
+    s.version = '0.0.0'
+    s.summary = 'dummy gem for pre-commit hooks'
+    s.authors = ['Anthony Sottile']
+end
diff --git a/pre_commit/resources/empty_template_setup.py b/pre_commit/resources/empty_template_setup.py
new file mode 100644
index 0000000..6886064
--- /dev/null
+++ b/pre_commit/resources/empty_template_setup.py
@@ -0,0 +1,4 @@
+from setuptools import setup
+
+
+setup(name='pre-commit-dummy-package', version='0.0.0')
diff --git a/pre_commit/resources/hook-tmpl b/pre_commit/resources/hook-tmpl
new file mode 100755
index 0000000..299144e
--- /dev/null
+++ b/pre_commit/resources/hook-tmpl
@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+# File generated by pre-commit: https://pre-commit.com
+# ID: 138fd403232d2ddd5efb44317e38bf03
+import os
+import sys
+
+# we try our best, but the shebang of this script is difficult to determine:
+# - macos doesn't ship with python3
+# - windows executables are almost always `python.exe`
+# therefore we continue to support python2 for this small script
+if sys.version_info < (3, 3):
+    from distutils.spawn import find_executable as which
+else:
+    from shutil import which
+
+# work around https://github.com/Homebrew/homebrew-core/issues/30445
+os.environ.pop('__PYVENV_LAUNCHER__', None)
+
+# start templated
+INSTALL_PYTHON = ''
+ARGS = ['hook-impl']
+# end templated
+ARGS.extend(('--hook-dir', os.path.realpath(os.path.dirname(__file__))))
+ARGS.append('--')
+ARGS.extend(sys.argv[1:])
+
+DNE = '`pre-commit` not found.  Did you forget to activate your virtualenv?'
+if os.access(INSTALL_PYTHON, os.X_OK):
+    CMD = [INSTALL_PYTHON, '-mpre_commit']
+elif which('pre-commit'):
+    CMD = ['pre-commit']
+else:
+    raise SystemExit(DNE)
+
+CMD.extend(ARGS)
+if sys.platform == 'win32':  # https://bugs.python.org/issue19124
+    import subprocess
+
+    if sys.version_info < (3, 7):  # https://bugs.python.org/issue25942
+        raise SystemExit(subprocess.Popen(CMD).wait())
+    else:
+        raise SystemExit(subprocess.call(CMD))
+else:
+    os.execvp(CMD[0], CMD)
diff --git a/pre_commit/resources/rbenv.tar.gz b/pre_commit/resources/rbenv.tar.gz
new file mode 100644
index 0000000..5307b19
--- /dev/null
+++ b/pre_commit/resources/rbenv.tar.gz
diff --git a/pre_commit/resources/ruby-build.tar.gz b/pre_commit/resources/ruby-build.tar.gz
new file mode 100644
index 0000000..4a69a09
--- /dev/null
+++ b/pre_commit/resources/ruby-build.tar.gz
diff --git a/pre_commit/resources/ruby-download.tar.gz b/pre_commit/resources/ruby-download.tar.gz
new file mode 100644
index 0000000..7ccfb6c
--- /dev/null
+++ b/pre_commit/resources/ruby-download.tar.gz
diff --git a/pre_commit/staged_files_only.py b/pre_commit/staged_files_only.py
new file mode 100644
index 0000000..09d323d
--- /dev/null
+++ b/pre_commit/staged_files_only.py
@@ -0,0 +1,90 @@
+import contextlib
+import logging
+import os.path
+import time
+from typing import Generator
+
+from pre_commit import git
+from pre_commit.util import CalledProcessError
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+from pre_commit.xargs import xargs
+
+
+logger = logging.getLogger('pre_commit')
+
+
+def _git_apply(patch: str) -> None:
+    args = ('apply', '--whitespace=nowarn', patch)
+    try:
+        cmd_output_b('git', *args)
+    except CalledProcessError:
+        # Retry with autocrlf=false -- see #570
+        cmd_output_b('git', '-c', 'core.autocrlf=false', *args)
+
+
+@contextlib.contextmanager
+def _intent_to_add_cleared() -> Generator[None, None, None]:
+    intent_to_add = git.intent_to_add_files()
+    if intent_to_add:
+        logger.warning('Unstaged intent-to-add files detected.')
+
+        xargs(('git', 'rm', '--cached', '--'), intent_to_add)
+        try:
+            yield
+        finally:
+            xargs(('git', 'add', '--intent-to-add', '--'), intent_to_add)
+    else:
+        yield
+
+
+@contextlib.contextmanager
+def _unstaged_changes_cleared(patch_dir: str) -> Generator[None, None, None]:
+    tree = cmd_output('git', 'write-tree')[1].strip()
+    retcode, diff_stdout_binary, _ = cmd_output_b(
+        'git', 'diff-index', '--ignore-submodules', '--binary',
+        '--exit-code', '--no-color', '--no-ext-diff', tree, '--',
+        retcode=None,
+    )
+    if retcode and diff_stdout_binary.strip():
+        patch_filename = f'patch{int(time.time())}'
+        patch_filename = os.path.join(patch_dir, patch_filename)
+        logger.warning('Unstaged files detected.')
+        logger.info(f'Stashing unstaged files to {patch_filename}.')
+        # Save the current unstaged changes as a patch
+        os.makedirs(patch_dir, exist_ok=True)
+        with open(patch_filename, 'wb') as patch_file:
+            patch_file.write(diff_stdout_binary)
+
+        # Clear the working directory of unstaged changes
+        cmd_output_b('git', 'checkout', '--', '.')
+        try:
+            yield
+        finally:
+            # Try to apply the patch we saved
+            try:
+                _git_apply(patch_filename)
+            except CalledProcessError:
+                logger.warning(
+                    'Stashed changes conflicted with hook auto-fixes... '
+                    'Rolling back fixes...',
+                )
+                # We failed to apply the patch, presumably due to fixes made
+                # by hooks.
+                # Roll back the changes made by hooks.
+                cmd_output_b('git', 'checkout', '--', '.')
+                _git_apply(patch_filename)
+            logger.info(f'Restored changes from {patch_filename}.')
+    else:
+        # There weren't any staged files so we don't need to do anything
+        # special
+        yield
+
+
+@contextlib.contextmanager
+def staged_files_only(patch_dir: str) -> Generator[None, None, None]:
+    """Clear any unstaged changes from the git working directory inside this
+    context.
+    """
+    with _intent_to_add_cleared(), _unstaged_changes_cleared(patch_dir):
+        yield
diff --git a/pre_commit/store.py b/pre_commit/store.py
new file mode 100644
index 0000000..760b37a
--- /dev/null
+++ b/pre_commit/store.py
@@ -0,0 +1,250 @@
+import contextlib
+import logging
+import os.path
+import sqlite3
+import tempfile
+from typing import Callable
+from typing import Generator
+from typing import List
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit import file_lock
+from pre_commit import git
+from pre_commit.util import CalledProcessError
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output_b
+from pre_commit.util import resource_text
+from pre_commit.util import rmtree
+
+
+logger = logging.getLogger('pre_commit')
+
+
+def _get_default_directory() -> str:
+    """Returns the default directory for the Store.  This is intentionally
+    underscored to indicate that `Store.get_default_directory` is the intended
+    way to get this information.  This is also done so
+    `Store.get_default_directory` can be mocked in tests and
+    `_get_default_directory` can be tested.
+    """
+    return os.environ.get('PRE_COMMIT_HOME') or os.path.join(
+        os.environ.get('XDG_CACHE_HOME') or os.path.expanduser('~/.cache'),
+        'pre-commit',
+    )
+
+
+class Store:
+    get_default_directory = staticmethod(_get_default_directory)
+
+    def __init__(self, directory: Optional[str] = None) -> None:
+        self.directory = directory or Store.get_default_directory()
+        self.db_path = os.path.join(self.directory, 'db.db')
+
+        if not os.path.exists(self.directory):
+            os.makedirs(self.directory, exist_ok=True)
+            with open(os.path.join(self.directory, 'README'), 'w') as f:
+                f.write(
+                    'This directory is maintained by the pre-commit project.\n'
+                    'Learn more: https://github.com/pre-commit/pre-commit\n',
+                )
+
+        if os.path.exists(self.db_path):
+            return
+        with self.exclusive_lock():
+            # Another process may have already completed this work
+            if os.path.exists(self.db_path):  # pragma: no cover (race)
+                return
+            # To avoid a race where someone ^Cs between db creation and
+            # execution of the CREATE TABLE statement
+            fd, tmpfile = tempfile.mkstemp(dir=self.directory)
+            # We'll be managing this file ourselves
+            os.close(fd)
+            with self.connect(db_path=tmpfile) as db:
+                db.executescript(
+                    'CREATE TABLE repos ('
+                    '    repo TEXT NOT NULL,'
+                    '    ref TEXT NOT NULL,'
+                    '    path TEXT NOT NULL,'
+                    '    PRIMARY KEY (repo, ref)'
+                    ');',
+                )
+                self._create_config_table(db)
+
+            # Atomic file move
+            os.rename(tmpfile, self.db_path)
+
+    @contextlib.contextmanager
+    def exclusive_lock(self) -> Generator[None, None, None]:
+        def blocked_cb() -> None:  # pragma: no cover (tests are in-process)
+            logger.info('Locking pre-commit directory')
+
+        with file_lock.lock(os.path.join(self.directory, '.lock'), blocked_cb):
+            yield
+
+    @contextlib.contextmanager
+    def connect(
+            self,
+            db_path: Optional[str] = None,
+    ) -> Generator[sqlite3.Connection, None, None]:
+        db_path = db_path or self.db_path
+        # sqlite doesn't close its fd with its contextmanager >.<
+        # contextlib.closing fixes this.
+        # See: https://stackoverflow.com/a/28032829/812183
+        with contextlib.closing(sqlite3.connect(db_path)) as db:
+            # this creates a transaction
+            with db:
+                yield db
+
+    @classmethod
+    def db_repo_name(cls, repo: str, deps: Sequence[str]) -> str:
+        if deps:
+            return f'{repo}:{",".join(sorted(deps))}'
+        else:
+            return repo
+
+    def _new_repo(
+            self,
+            repo: str,
+            ref: str,
+            deps: Sequence[str],
+            make_strategy: Callable[[str], None],
+    ) -> str:
+        repo = self.db_repo_name(repo, deps)
+
+        def _get_result() -> Optional[str]:
+            # Check if we already exist
+            with self.connect() as db:
+                result = db.execute(
+                    'SELECT path FROM repos WHERE repo = ? AND ref = ?',
+                    (repo, ref),
+                ).fetchone()
+                return result[0] if result else None
+
+        result = _get_result()
+        if result:
+            return result
+        with self.exclusive_lock():
+            # Another process may have already completed this work
+            result = _get_result()
+            if result:  # pragma: no cover (race)
+                return result
+
+            logger.info(f'Initializing environment for {repo}.')
+
+            directory = tempfile.mkdtemp(prefix='repo', dir=self.directory)
+            with clean_path_on_failure(directory):
+                make_strategy(directory)
+
+            # Update our db with the created repo
+            with self.connect() as db:
+                db.execute(
+                    'INSERT INTO repos (repo, ref, path) VALUES (?, ?, ?)',
+                    [repo, ref, directory],
+                )
+        return directory
+
+    def _complete_clone(self, ref: str, git_cmd: Callable[..., None]) -> None:
+        """Perform a complete clone of a repository and its submodules """
+
+        git_cmd('fetch', 'origin', '--tags')
+        git_cmd('checkout', ref)
+        git_cmd('submodule', 'update', '--init', '--recursive')
+
+    def _shallow_clone(self, ref: str, git_cmd: Callable[..., None]) -> None:
+        """Perform a shallow clone of a repository and its submodules """
+
+        git_config = 'protocol.version=2'
+        git_cmd('-c', git_config, 'fetch', 'origin', ref, '--depth=1')
+        git_cmd('checkout', 'FETCH_HEAD')
+        git_cmd(
+            '-c', git_config, 'submodule', 'update', '--init', '--recursive',
+            '--depth=1',
+        )
+
+    def clone(self, repo: str, ref: str, deps: Sequence[str] = ()) -> str:
+        """Clone the given url and checkout the specific ref."""
+
+        def clone_strategy(directory: str) -> None:
+            git.init_repo(directory, repo)
+            env = git.no_git_env()
+
+            def _git_cmd(*args: str) -> None:
+                cmd_output_b('git', *args, cwd=directory, env=env)
+
+            try:
+                self._shallow_clone(ref, _git_cmd)
+            except CalledProcessError:
+                self._complete_clone(ref, _git_cmd)
+
+        return self._new_repo(repo, ref, deps, clone_strategy)
+
+    LOCAL_RESOURCES = (
+        'Cargo.toml', 'main.go', 'main.rs', '.npmignore', 'package.json',
+        'pre_commit_dummy_package.gemspec', 'setup.py', 'environment.yml',
+        'Makefile.PL',
+    )
+
+    def make_local(self, deps: Sequence[str]) -> str:
+        def make_local_strategy(directory: str) -> None:
+            for resource in self.LOCAL_RESOURCES:
+                contents = resource_text(f'empty_template_{resource}')
+                with open(os.path.join(directory, resource), 'w') as f:
+                    f.write(contents)
+
+            env = git.no_git_env()
+
+            # initialize the git repository so it looks more like cloned repos
+            def _git_cmd(*args: str) -> None:
+                cmd_output_b('git', *args, cwd=directory, env=env)
+
+            git.init_repo(directory, '<<unknown>>')
+            _git_cmd('add', '.')
+            git.commit(repo=directory)
+
+        return self._new_repo(
+            'local', C.LOCAL_REPO_VERSION, deps, make_local_strategy,
+        )
+
+    def _create_config_table(self, db: sqlite3.Connection) -> None:
+        db.executescript(
+            'CREATE TABLE IF NOT EXISTS configs ('
+            '   path TEXT NOT NULL,'
+            '   PRIMARY KEY (path)'
+            ');',
+        )
+
+    def mark_config_used(self, path: str) -> None:
+        path = os.path.realpath(path)
+        # don't insert config files that do not exist
+        if not os.path.exists(path):
+            return
+        with self.connect() as db:
+            # TODO: eventually remove this and only create in _create
+            self._create_config_table(db)
+            db.execute('INSERT OR IGNORE INTO configs VALUES (?)', (path,))
+
+    def select_all_configs(self) -> List[str]:
+        with self.connect() as db:
+            self._create_config_table(db)
+            rows = db.execute('SELECT path FROM configs').fetchall()
+            return [path for path, in rows]
+
+    def delete_configs(self, configs: List[str]) -> None:
+        with self.connect() as db:
+            rows = [(path,) for path in configs]
+            db.executemany('DELETE FROM configs WHERE path = ?', rows)
+
+    def select_all_repos(self) -> List[Tuple[str, str, str]]:
+        with self.connect() as db:
+            return db.execute('SELECT repo, ref, path from repos').fetchall()
+
+    def delete_repo(self, db_repo_name: str, ref: str, path: str) -> None:
+        with self.connect() as db:
+            db.execute(
+                'DELETE FROM repos WHERE repo = ? and ref = ?',
+                (db_repo_name, ref),
+            )
+        rmtree(path)
diff --git a/pre_commit/util.py b/pre_commit/util.py
new file mode 100644
index 0000000..2db579a
--- /dev/null
+++ b/pre_commit/util.py
@@ -0,0 +1,272 @@
+import contextlib
+import errno
+import functools
+import os.path
+import shutil
+import stat
+import subprocess
+import sys
+import tempfile
+from types import TracebackType
+from typing import Any
+from typing import Callable
+from typing import Dict
+from typing import Generator
+from typing import IO
+from typing import Optional
+from typing import Tuple
+from typing import Type
+from typing import Union
+
+import yaml
+
+from pre_commit import parse_shebang
+
+if sys.version_info >= (3, 7):  # pragma: no cover (PY37+)
+    from importlib.resources import open_binary
+    from importlib.resources import read_text
+else:  # pragma: no cover (<PY37)
+    from importlib_resources import open_binary
+    from importlib_resources import read_text
+
+EnvironT = Union[Dict[str, str], 'os._Environ']
+
+Loader = getattr(yaml, 'CSafeLoader', yaml.SafeLoader)
+yaml_load = functools.partial(yaml.load, Loader=Loader)
+Dumper = getattr(yaml, 'CSafeDumper', yaml.SafeDumper)
+
+
+def yaml_dump(o: Any) -> str:
+    # when python/mypy#1484 is solved, this can be `functools.partial`
+    return yaml.dump(
+        o, Dumper=Dumper, default_flow_style=False, indent=4, sort_keys=False,
+    )
+
+
+def force_bytes(exc: Any) -> bytes:
+    with contextlib.suppress(TypeError):
+        return bytes(exc)
+    with contextlib.suppress(Exception):
+        return str(exc).encode()
+    return f'<unprintable {type(exc).__name__} object>'.encode()
+
+
+@contextlib.contextmanager
+def clean_path_on_failure(path: str) -> Generator[None, None, None]:
+    """Cleans up the directory on an exceptional failure."""
+    try:
+        yield
+    except BaseException:
+        if os.path.exists(path):
+            rmtree(path)
+        raise
+
+
+@contextlib.contextmanager
+def tmpdir() -> Generator[str, None, None]:
+    """Contextmanager to create a temporary directory.  It will be cleaned up
+    afterwards.
+    """
+    tempdir = tempfile.mkdtemp()
+    try:
+        yield tempdir
+    finally:
+        rmtree(tempdir)
+
+
+def resource_bytesio(filename: str) -> IO[bytes]:
+    return open_binary('pre_commit.resources', filename)
+
+
+def resource_text(filename: str) -> str:
+    return read_text('pre_commit.resources', filename)
+
+
+def make_executable(filename: str) -> None:
+    original_mode = os.stat(filename).st_mode
+    new_mode = original_mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
+    os.chmod(filename, new_mode)
+
+
+class CalledProcessError(RuntimeError):
+    def __init__(
+            self,
+            returncode: int,
+            cmd: Tuple[str, ...],
+            expected_returncode: int,
+            stdout: bytes,
+            stderr: Optional[bytes],
+    ) -> None:
+        super().__init__(returncode, cmd, expected_returncode, stdout, stderr)
+        self.returncode = returncode
+        self.cmd = cmd
+        self.expected_returncode = expected_returncode
+        self.stdout = stdout
+        self.stderr = stderr
+
+    def __bytes__(self) -> bytes:
+        def _indent_or_none(part: Optional[bytes]) -> bytes:
+            if part:
+                return b'\n    ' + part.replace(b'\n', b'\n    ')
+            else:
+                return b' (none)'
+
+        return b''.join((
+            f'command: {self.cmd!r}\n'.encode(),
+            f'return code: {self.returncode}\n'.encode(),
+            f'expected return code: {self.expected_returncode}\n'.encode(),
+            b'stdout:', _indent_or_none(self.stdout), b'\n',
+            b'stderr:', _indent_or_none(self.stderr),
+        ))
+
+    def __str__(self) -> str:
+        return self.__bytes__().decode()
+
+
+def _setdefault_kwargs(kwargs: Dict[str, Any]) -> None:
+    for arg in ('stdin', 'stdout', 'stderr'):
+        kwargs.setdefault(arg, subprocess.PIPE)
+
+
+def _oserror_to_output(e: OSError) -> Tuple[int, bytes, None]:
+    return 1, force_bytes(e).rstrip(b'\n') + b'\n', None
+
+
+def cmd_output_b(
+        *cmd: str,
+        retcode: Optional[int] = 0,
+        **kwargs: Any,
+) -> Tuple[int, bytes, Optional[bytes]]:
+    _setdefault_kwargs(kwargs)
+
+    try:
+        cmd = parse_shebang.normalize_cmd(cmd)
+    except parse_shebang.ExecutableNotFoundError as e:
+        returncode, stdout_b, stderr_b = e.to_output()
+    else:
+        try:
+            proc = subprocess.Popen(cmd, **kwargs)
+        except OSError as e:
+            returncode, stdout_b, stderr_b = _oserror_to_output(e)
+        else:
+            stdout_b, stderr_b = proc.communicate()
+            returncode = proc.returncode
+
+    if retcode is not None and retcode != returncode:
+        raise CalledProcessError(returncode, cmd, retcode, stdout_b, stderr_b)
+
+    return returncode, stdout_b, stderr_b
+
+
+def cmd_output(*cmd: str, **kwargs: Any) -> Tuple[int, str, Optional[str]]:
+    returncode, stdout_b, stderr_b = cmd_output_b(*cmd, **kwargs)
+    stdout = stdout_b.decode() if stdout_b is not None else None
+    stderr = stderr_b.decode() if stderr_b is not None else None
+    return returncode, stdout, stderr
+
+
+if os.name != 'nt':  # pragma: win32 no cover
+    from os import openpty
+    import termios
+
+    class Pty:
+        def __init__(self) -> None:
+            self.r: Optional[int] = None
+            self.w: Optional[int] = None
+
+        def __enter__(self) -> 'Pty':
+            self.r, self.w = openpty()
+
+            # tty flags normally change \n to \r\n
+            attrs = termios.tcgetattr(self.r)
+            assert isinstance(attrs[1], int)
+            attrs[1] &= ~(termios.ONLCR | termios.OPOST)
+            termios.tcsetattr(self.r, termios.TCSANOW, attrs)
+
+            return self
+
+        def close_w(self) -> None:
+            if self.w is not None:
+                os.close(self.w)
+                self.w = None
+
+        def close_r(self) -> None:
+            assert self.r is not None
+            os.close(self.r)
+            self.r = None
+
+        def __exit__(
+                self,
+                exc_type: Optional[Type[BaseException]],
+                exc_value: Optional[BaseException],
+                traceback: Optional[TracebackType],
+        ) -> None:
+            self.close_w()
+            self.close_r()
+
+    def cmd_output_p(
+            *cmd: str,
+            retcode: Optional[int] = 0,
+            **kwargs: Any,
+    ) -> Tuple[int, bytes, Optional[bytes]]:
+        assert retcode is None
+        assert kwargs['stderr'] == subprocess.STDOUT, kwargs['stderr']
+        _setdefault_kwargs(kwargs)
+
+        try:
+            cmd = parse_shebang.normalize_cmd(cmd)
+        except parse_shebang.ExecutableNotFoundError as e:
+            return e.to_output()
+
+        with open(os.devnull) as devnull, Pty() as pty:
+            assert pty.r is not None
+            kwargs.update({'stdin': devnull, 'stdout': pty.w, 'stderr': pty.w})
+            try:
+                proc = subprocess.Popen(cmd, **kwargs)
+            except OSError as e:
+                return _oserror_to_output(e)
+
+            pty.close_w()
+
+            buf = b''
+            while True:
+                try:
+                    bts = os.read(pty.r, 4096)
+                except OSError as e:
+                    if e.errno == errno.EIO:
+                        bts = b''
+                    else:
+                        raise
+                else:
+                    buf += bts
+                if not bts:
+                    break
+
+        return proc.wait(), buf, None
+else:  # pragma: no cover
+    cmd_output_p = cmd_output_b
+
+
+def rmtree(path: str) -> None:
+    """On windows, rmtree fails for readonly dirs."""
+    def handle_remove_readonly(
+            func: Callable[..., Any],
+            path: str,
+            exc: Tuple[Type[OSError], OSError, TracebackType],
+    ) -> None:
+        excvalue = exc[1]
+        if (
+                func in (os.rmdir, os.remove, os.unlink) and
+                excvalue.errno == errno.EACCES
+        ):
+            for p in (path, os.path.dirname(path)):
+                os.chmod(p, os.stat(p).st_mode | stat.S_IWUSR)
+            func(path)
+        else:
+            raise
+    shutil.rmtree(path, ignore_errors=False, onerror=handle_remove_readonly)
+
+
+def parse_version(s: str) -> Tuple[int, ...]:
+    """poor man's version comparison"""
+    return tuple(int(p) for p in s.split('.'))
diff --git a/pre_commit/xargs.py b/pre_commit/xargs.py
new file mode 100644
index 0000000..5235dc6
--- /dev/null
+++ b/pre_commit/xargs.py
@@ -0,0 +1,157 @@
+import concurrent.futures
+import contextlib
+import math
+import os
+import subprocess
+import sys
+from typing import Any
+from typing import Callable
+from typing import Generator
+from typing import Iterable
+from typing import List
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+from typing import TypeVar
+
+from pre_commit import parse_shebang
+from pre_commit.util import cmd_output_b
+from pre_commit.util import cmd_output_p
+from pre_commit.util import EnvironT
+
+TArg = TypeVar('TArg')
+TRet = TypeVar('TRet')
+
+
+def _environ_size(_env: Optional[EnvironT] = None) -> int:
+    environ = _env if _env is not None else getattr(os, 'environb', os.environ)
+    size = 8 * len(environ)  # number of pointers in `envp`
+    for k, v in environ.items():
+        size += len(k) + len(v) + 2  # c strings in `envp`
+    return size
+
+
+def _get_platform_max_length() -> int:  # pragma: no cover (platform specific)
+    if os.name == 'posix':
+        maximum = os.sysconf('SC_ARG_MAX') - 2048 - _environ_size()
+        maximum = max(min(maximum, 2 ** 17), 2 ** 12)
+        return maximum
+    elif os.name == 'nt':
+        return 2 ** 15 - 2048  # UNICODE_STRING max - headroom
+    else:
+        # posix minimum
+        return 2 ** 12
+
+
+def _command_length(*cmd: str) -> int:
+    full_cmd = ' '.join(cmd)
+
+    # win32 uses the amount of characters, more details at:
+    # https://github.com/pre-commit/pre-commit/pull/839
+    if sys.platform == 'win32':
+        return len(full_cmd.encode('utf-16le')) // 2
+    else:
+        return len(full_cmd.encode(sys.getfilesystemencoding()))
+
+
+class ArgumentTooLongError(RuntimeError):
+    pass
+
+
+def partition(
+        cmd: Sequence[str],
+        varargs: Sequence[str],
+        target_concurrency: int,
+        _max_length: Optional[int] = None,
+) -> Tuple[Tuple[str, ...], ...]:
+    _max_length = _max_length or _get_platform_max_length()
+
+    # Generally, we try to partition evenly into at least `target_concurrency`
+    # partitions, but we don't want a bunch of tiny partitions.
+    max_args = max(4, math.ceil(len(varargs) / target_concurrency))
+
+    cmd = tuple(cmd)
+    ret = []
+
+    ret_cmd: List[str] = []
+    # Reversed so arguments are in order
+    varargs = list(reversed(varargs))
+
+    total_length = _command_length(*cmd) + 1
+    while varargs:
+        arg = varargs.pop()
+
+        arg_length = _command_length(arg) + 1
+        if (
+                total_length + arg_length <= _max_length and
+                len(ret_cmd) < max_args
+        ):
+            ret_cmd.append(arg)
+            total_length += arg_length
+        elif not ret_cmd:
+            raise ArgumentTooLongError(arg)
+        else:
+            # We've exceeded the length, yield a command
+            ret.append(cmd + tuple(ret_cmd))
+            ret_cmd = []
+            total_length = _command_length(*cmd) + 1
+            varargs.append(arg)
+
+    ret.append(cmd + tuple(ret_cmd))
+
+    return tuple(ret)
+
+
+@contextlib.contextmanager
+def _thread_mapper(maxsize: int) -> Generator[
+    Callable[[Callable[[TArg], TRet], Iterable[TArg]], Iterable[TRet]],
+    None, None,
+]:
+    if maxsize == 1:
+        yield map
+    else:
+        with concurrent.futures.ThreadPoolExecutor(maxsize) as ex:
+            yield ex.map
+
+
+def xargs(
+        cmd: Tuple[str, ...],
+        varargs: Sequence[str],
+        *,
+        color: bool = False,
+        target_concurrency: int = 1,
+        _max_length: int = _get_platform_max_length(),
+        **kwargs: Any,
+) -> Tuple[int, bytes]:
+    """A simplified implementation of xargs.
+
+    color: Make a pty if on a platform that supports it
+    target_concurrency: Target number of partitions to run concurrently
+    """
+    cmd_fn = cmd_output_p if color else cmd_output_b
+    retcode = 0
+    stdout = b''
+
+    try:
+        cmd = parse_shebang.normalize_cmd(cmd)
+    except parse_shebang.ExecutableNotFoundError as e:
+        return e.to_output()[:2]
+
+    partitions = partition(cmd, varargs, target_concurrency, _max_length)
+
+    def run_cmd_partition(
+            run_cmd: Tuple[str, ...],
+    ) -> Tuple[int, bytes, Optional[bytes]]:
+        return cmd_fn(
+            *run_cmd, retcode=None, stderr=subprocess.STDOUT, **kwargs,
+        )
+
+    threads = min(len(partitions), target_concurrency)
+    with _thread_mapper(threads) as thread_map:
+        results = thread_map(run_cmd_partition, partitions)
+
+        for proc_retcode, proc_out, _ in results:
+            retcode = max(retcode, proc_retcode)
+            stdout += proc_out
+
+    return retcode, stdout