add --force option for presubmit command

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
 import json
@@ skipping 908 matching lines @@
     log_args = [args[0] + '..' + args[1]]
   else:
     log_args = args[:]  # Hope for the best!
   return RunGit(['log', '--pretty=format:%s\n\n%b'] + log_args)
 
 
 def CMDpresubmit(parser, args):
   """run presubmit tests on the current changelist"""
   parser.add_option('--upload', action='store_true',
                     help='Run upload hook instead of the push/dcommit hook')
+  parser.add_option('--force', action='store_true',
+                    help='Run checks even if tree is dirty')
   (options, args) = parser.parse_args(args)
 
   # Make sure index is up-to-date before running diff-index.
   RunGit(['update-index', '--refresh', '-q'], error_ok=True)
-  if RunGit(['diff-index', 'HEAD']):
+  if not options.force and RunGit(['diff-index', 'HEAD']):
     # TODO(maruel): Is this really necessary?
-    print 'Cannot presubmit with a dirty tree.  You must commit locally first.'
+    print ('Cannot presubmit with a dirty tree.\n'
+          'You must commit locally first (or use --force).')
     return 1
 
   cl = Changelist()
   if args:
     base_branch = args[0]
   else:
     # Default to diffing against the "upstream" branch.
     base_branch = cl.GetUpstreamBranch()
 
   cl.RunHook(committing=not options.upload, upstream_branch=base_branch,
@@ skipping 664 matching lines @@
              'and retry or visit go/isgaeup.\n%s') % (e.code, str(e)))
 
   # Not a known command. Default to help.
   GenUsage(parser, 'help')
   return CMDhelp(parser, argv)
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   sys.exit(main(sys.argv[1:]))