Add option to run from alternate config file

pre_commit/main.py

@@ -34,6 +34,10 @@ def _add_color_option(parser):
     )
 
 
+def _add_config_option(parser):
+    parser.add_argument('-c', '--config', help='Path to alternate config file')
+
+
 def main(argv=None):
     argv = argv if argv is not None else sys.argv[1:]
     argv = [five.to_text(arg) for arg in argv]
@@ -89,6 +93,7 @@ def main(argv=None):
         help="Auto-update pre-commit config to the latest repos' versions.",
     )
     _add_color_option(autoupdate_parser)
+    _add_config_option(autoupdate_parser)
 
     run_parser = subparsers.add_parser('run', help='Run hooks.')
     _add_color_option(run_parser)
@@ -119,6 +124,8 @@ def main(argv=None):
         '--hook-stage', choices=('commit', 'push'), default='commit',
         help='The stage during which the hook is fired e.g. commit or push.',
     )
+    _add_config_option(run_parser)
+
     run_mutex_group = run_parser.add_mutually_exclusive_group(required=False)
     run_mutex_group.add_argument(
         '--all-files', '-a', action='store_true', default=False,