Add extra args to prepare-commit-msg

pre_commit/commands/hook_impl.py

@@ -76,6 +76,8 @@ def _ns(
         remote_name: str | None = None,
         remote_url: str | None = None,
         commit_msg_filename: str | None = None,
+        commit_msg: str | None = None,
+        commit_sha: str | None = None,
         checkout_type: str | None = None,
         is_squash_merge: str | None = None,
         rewrite_command: str | None = None,
@@ -90,6 +92,8 @@ def _ns(
         remote_name=remote_name,
         remote_url=remote_url,
         commit_msg_filename=commit_msg_filename,
+        commit_msg=commit_msg,
+        commit_sha=commit_sha,
         all_files=all_files,
         checkout_type=checkout_type,
         is_squash_merge=is_squash_merge,
@@ -202,8 +206,20 @@ def _run_ns(
     _check_args_length(hook_type, args)
     if hook_type == 'pre-push':
         return _pre_push_ns(color, args, stdin)
-    elif hook_type in {'commit-msg', 'prepare-commit-msg'}:
+    elif hook_type in 'commit-msg' or hook_type == 'prepare-commit-msg' and \
+            len(args) == 1:
         return _ns(hook_type, color, commit_msg_filename=args[0])
+    elif hook_type == 'prepare-commit-msg' and len(args) > 1:
+        if (len(args) == 2):
+            return _ns(
+                hook_type, color, commit_msg_filename=args[0],
+                commit_msg=args[1],
+            )
+        else:
+            return _ns(
+                hook_type, color, commit_msg_filename=args[0],
+                commit_msg=args[1], commit_sha=args[2],
+            )
     elif hook_type in {'post-commit', 'pre-merge-commit', 'pre-commit'}:
         return _ns(hook_type, color)
     elif hook_type == 'post-checkout':

pre_commit/commands/run.py

@@ -361,6 +361,13 @@ def run(
     ):
         return 0
 
+    # Expose commit_msg / commit_sha as environment variables for the hooks
+    if args.commit_msg:
+        environ['PRE_COMMIT_COMMIT_MSG'] = args.commit_msg
+
+    if args.commit_sha:
+        environ['PRE_COMMIT_COMMIT_SHA'] = args.commit_sha
+
     # Expose from-ref / to-ref as environment variables for hooks to consume
     if args.from_ref and args.to_ref:
         # legacy names