3 files changed, 11 insertions, 5 deletions
diff --git a/pre_commit/commands/hook_impl.py b/pre_commit/commands/hook_impl.py
index c544167..90bb33b 100644
--- a/pre_commit/commands/hook_impl.py
+++ b/pre_commit/commands/hook_impl.py
@@ -78,6 +78,7 @@ def _ns(
         commit_msg_filename: Optional[str] = None,
         checkout_type: Optional[str] = None,
         is_squash_merge: Optional[str] = None,
+        rewrite_command: Optional[str] = None,
 ) -> argparse.Namespace:
     return argparse.Namespace(
         color=color,
@@ -92,6 +93,7 @@ def _ns(
         all_files=all_files,
         checkout_type=checkout_type,
         is_squash_merge=is_squash_merge,
+        rewrite_command=rewrite_command,
         files=(),
         hook=None,
         verbose=False,
@@ -166,6 +168,7 @@ _EXPECTED_ARG_LENGTH_BY_HOOK = {
     'pre-commit': 0,
     'pre-merge-commit': 0,
     'post-merge': 1,
+    'post-rewrite': 1,
     'pre-push': 2,
 }
 
@@ -209,6 +212,8 @@ def _run_ns(
         )
     elif hook_type == 'post-merge':
         return _ns(hook_type, color, is_squash_merge=args[0])
+    elif hook_type == 'post-rewrite':
+        return _ns(hook_type, color, rewrite_command=args[0])
     else:
         raise AssertionError(f'unexpected hook type: {hook_type}')
 
diff --git a/pre_commit/commands/migrate_config.py b/pre_commit/commands/migrate_config.py
index a155f6b..fef14cd 100644
--- a/pre_commit/commands/migrate_config.py
+++ b/pre_commit/commands/migrate_config.py
@@ -3,7 +3,6 @@ import textwrap
 
 import yaml
 
-from pre_commit.clientlib import load_config
 from pre_commit.util import yaml_load
 
 
@@ -40,9 +39,6 @@ def _migrate_sha_to_rev(contents: str) -> str:
 
 
 def migrate_config(config_file: str, quiet: bool = False) -> int:
-    # ensure that the configuration is a valid pre-commit configuration
-    load_config(config_file)
-
     with open(config_file) as f:
         orig_contents = contents = f.read()
 
diff --git a/pre_commit/commands/run.py b/pre_commit/commands/run.py
index d906d5b..95ad5e9 100644
--- a/pre_commit/commands/run.py
+++ b/pre_commit/commands/run.py
@@ -245,7 +245,9 @@ def _compute_cols(hooks: Sequence[Hook]) -> int:
 
 def _all_filenames(args: argparse.Namespace) -> Collection[str]:
     # these hooks do not operate on files
-    if args.hook_stage in {'post-checkout', 'post-commit', 'post-merge'}:
+    if args.hook_stage in {
+        'post-checkout', 'post-commit', 'post-merge', 'post-rewrite',
+    }:
         return ()
     elif args.hook_stage in {'prepare-commit-msg', 'commit-msg'}:
         return (args.commit_msg_filename,)
@@ -386,6 +388,9 @@ def run(
     if args.is_squash_merge:
         environ['PRE_COMMIT_IS_SQUASH_MERGE'] = args.is_squash_merge
 
+    if args.rewrite_command:
+        environ['PRE_COMMIT_REWRITE_COMMAND'] = args.rewrite_command
+
     # Set pre_commit flag
     environ['PRE_COMMIT'] = '1'