fix for #157

pre_commit/commands/run.py

@@ -139,6 +139,18 @@ def _has_unmerged_paths(runner):
     return bool(stdout.strip())
 
 
+def _has_unstaged_config(runner):
+    retcode, stdout, stderr = runner.cmd_runner.run(
+        [
+            'git', 'diff', '--exit-code', runner.config_file_path
+        ],
+        retcode=None,
+        encoding=None,
+    )
+    # be explicit, other git errors don't mean it has an unstaged config.
+    return retcode == 1
+
+
 def run(runner, args, write=sys_stdout_write_wrapper, environ=os.environ):
     # Set up our logging handler
     logger.addHandler(LoggingHandler(args.color, write=write))
@@ -151,6 +163,16 @@ def run(runner, args, write=sys_stdout_write_wrapper, environ=os.environ):
     if bool(args.source) != bool(args.origin):
         logger.error('Specify both --origin and --source.')
         return 1
+    if _has_unstaged_config(runner) and not args.no_stash:
+        if args.allow_unstaged_config:
+            logger.warn('You have an unstaged config file and have '
+                        'specified the --allow-unstaged-config option.\n'
+                        'Note that your config will be stashed before the '
+                        'config is parsed unless --no-stash is specified.')
+        else:
+            logger.error('You have an unstaged config file and have not '
+                         'specified the --allow-unstaged-config option.\n')
+            return 1
 
     # Don't stash if specified or files are specified
     if args.no_stash or args.all_files or args.files:

pre_commit/main.py

@@ -94,6 +94,11 @@ def main(argv=None):
         '--source', '-s',
         help='The remote branch"s commit_id when using `git push`',
     )
+    run_parser.add_argument(
+        '--allow-unstaged-config', default=False, action='store_true',
+        help='Allow an unstaged config to be present.  Note that this will'
+        'be stashed before parsing unless --no-stash is specified'
+    )
     run_mutex_group = run_parser.add_mutually_exclusive_group(required=False)
     run_mutex_group.add_argument(
         '--all-files', '-a', action='store_true', default=False,