Add pre-rebase hook support

pre_commit/clientlib.py

@@ -30,6 +30,7 @@ HOOK_TYPES = (
     'pre-commit',
     'pre-merge-commit',
     'pre-push',
+    'pre-rebase',
     'prepare-commit-msg',
 )
 # `manual` is not invoked by any installed git hook.  See #719

pre_commit/commands/hook_impl.py

@@ -73,6 +73,8 @@ def _ns(
         local_branch: str | None = None,
         from_ref: str | None = None,
         to_ref: str | None = None,
+        pre_rebase_upstream: str | None = None,
+        pre_rebase_branch: str | None = None,
         remote_name: str | None = None,
         remote_url: str | None = None,
         commit_msg_filename: str | None = None,
@@ -89,6 +91,8 @@ def _ns(
         local_branch=local_branch,
         from_ref=from_ref,
         to_ref=to_ref,
+        pre_rebase_upstream=pre_rebase_upstream,
+        pre_rebase_branch=pre_rebase_branch,
         remote_name=remote_name,
         remote_url=remote_url,
         commit_msg_filename=commit_msg_filename,
@@ -185,6 +189,12 @@ def _check_args_length(hook_type: str, args: Sequence[str]) -> None:
                 f'hook-impl for {hook_type} expected 1, 2, or 3 arguments '
                 f'but got {len(args)}: {args}',
             )
+    elif hook_type == 'pre-rebase':
+        if len(args) < 1 or len(args) > 2:
+            raise SystemExit(
+                f'hook-impl for {hook_type} expected 1 or 2 arguments '
+                f'but got {len(args)}: {args}',
+            )
     elif hook_type in _EXPECTED_ARG_LENGTH_BY_HOOK:
         expected = _EXPECTED_ARG_LENGTH_BY_HOOK[hook_type]
         if len(args) != expected:
@@ -231,6 +241,13 @@ def _run_ns(
         return _ns(hook_type, color, is_squash_merge=args[0])
     elif hook_type == 'post-rewrite':
         return _ns(hook_type, color, rewrite_command=args[0])
+    elif hook_type == 'pre-rebase' and len(args) == 1:
+        return _ns(hook_type, color, pre_rebase_upstream=args[0])
+    elif hook_type == 'pre-rebase' and len(args) == 2:
+        return _ns(
+            hook_type, color, pre_rebase_upstream=args[0],
+            pre_rebase_branch=args[1],
+        )
     else:
         raise AssertionError(f'unexpected hook type: {hook_type}')
 

pre_commit/commands/run.py

@@ -254,6 +254,7 @@ 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', 'post-rewrite',
+        'pre-rebase',
     }:
         return ()
     elif args.hook_stage in {'prepare-commit-msg', 'commit-msg'}:
@@ -389,6 +390,10 @@ def run(
         environ['PRE_COMMIT_FROM_REF'] = args.from_ref
         environ['PRE_COMMIT_TO_REF'] = args.to_ref
 
+    if args.pre_rebase_upstream and args.pre_rebase_branch:
+        environ['PRE_COMMIT_PRE_REBASE_UPSTREAM'] = args.pre_rebase_upstream
+        environ['PRE_COMMIT_PRE_REBASE_BRANCH'] = args.pre_rebase_branch
+
     if (
         args.remote_name and args.remote_url and
         args.remote_branch and args.local_branch

pre_commit/main.py

@@ -107,6 +107,17 @@ def _add_run_options(parser: argparse.ArgumentParser) -> None:
             'now checked out.'
         ),
     )
+    parser.add_argument(
+        '--pre-rebase-upstream', help=(
+            'The upstream from which the series was forked.'
+        ),
+    )
+    parser.add_argument(
+        '--pre-rebase-branch', help=(
+            'The branch being rebased, and is not set when  '
+            'rebasing the current branch.'
+        ),
+    )
     parser.add_argument(
         '--commit-msg-filename',
         help='Filename to check when running during `commit-msg`',