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-rw-r--r--pre_commit_hooks/destroyed_symlinks.py92
1 files changed, 92 insertions, 0 deletions
diff --git a/pre_commit_hooks/destroyed_symlinks.py b/pre_commit_hooks/destroyed_symlinks.py
new file mode 100644
index 0000000..f256908
--- /dev/null
+++ b/pre_commit_hooks/destroyed_symlinks.py
@@ -0,0 +1,92 @@
+from __future__ import annotations
+
+import argparse
+import shlex
+import subprocess
+from typing import Sequence
+
+from pre_commit_hooks.util import cmd_output
+from pre_commit_hooks.util import zsplit
+
+ORDINARY_CHANGED_ENTRIES_MARKER = '1'
+PERMS_LINK = '120000'
+PERMS_NONEXIST = '000000'
+
+
+def find_destroyed_symlinks(files: Sequence[str]) -> list[str]:
+ destroyed_links: list[str] = []
+ if not files:
+ return destroyed_links
+ for line in zsplit(
+ cmd_output('git', 'status', '--porcelain=v2', '-z', '--', *files),
+ ):
+ splitted = line.split(' ')
+ if splitted and splitted[0] == ORDINARY_CHANGED_ENTRIES_MARKER:
+ # https://git-scm.com/docs/git-status#_changed_tracked_entries
+ (
+ _, _, _,
+ mode_HEAD,
+ mode_index,
+ _,
+ hash_HEAD,
+ hash_index,
+ *path_splitted,
+ ) = splitted
+ path = ' '.join(path_splitted)
+ if (
+ mode_HEAD == PERMS_LINK and
+ mode_index != PERMS_LINK and
+ mode_index != PERMS_NONEXIST
+ ):
+ if hash_HEAD == hash_index:
+ # if old and new hashes are equal, it's not needed to check
+ # anything more, we've found a destroyed symlink for sure
+ destroyed_links.append(path)
+ else:
+ # if old and new hashes are *not* equal, it doesn't mean
+ # that everything is OK - new file may be altered
+ # by something like trailing-whitespace and/or
+ # mixed-line-ending hooks so we need to go deeper
+ SIZE_CMD = ('git', 'cat-file', '-s')
+ size_index = int(cmd_output(*SIZE_CMD, hash_index).strip())
+ size_HEAD = int(cmd_output(*SIZE_CMD, hash_HEAD).strip())
+
+ # in the worst case new file may have CRLF added
+ # so check content only if new file is bigger
+ # not more than 2 bytes compared to the old one
+ if size_index <= size_HEAD + 2:
+ head_content = subprocess.check_output(
+ ('git', 'cat-file', '-p', hash_HEAD),
+ ).rstrip()
+ index_content = subprocess.check_output(
+ ('git', 'cat-file', '-p', hash_index),
+ ).rstrip()
+ if head_content == index_content:
+ destroyed_links.append(path)
+ return destroyed_links
+
+
+def main(argv: Sequence[str] | None = None) -> int:
+ parser = argparse.ArgumentParser()
+ parser.add_argument('filenames', nargs='*', help='Filenames to check.')
+ args = parser.parse_args(argv)
+ destroyed_links = find_destroyed_symlinks(files=args.filenames)
+ if destroyed_links:
+ print('Destroyed symlinks:')
+ for destroyed_link in destroyed_links:
+ print(f'- {destroyed_link}')
+ print('You should unstage affected files:')
+ print(f'\tgit reset HEAD -- {shlex.join(destroyed_links)}')
+ print(
+ 'And retry commit. As a long term solution '
+ 'you may try to explicitly tell git that your '
+ 'environment does not support symlinks:',
+ )
+ print('\tgit config core.symlinks false')
+ return 1
+ else:
+ return 0
+
+
+if __name__ == '__main__':
+ raise SystemExit(main())