Auto-roll script: Add dirty tree check and git pull

tools/autoroller/roll_chromium_revision.py

 #!/usr/bin/env python
 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 """Script to roll chromium_revision in the WebRTC DEPS file."""
@@ skipping 280 matching lines @@
 
 
 def _CreateRollBranch(dry_run):
   current_branch = _RunCommand(
       ['git', 'rev-parse', '--abbrev-ref', 'HEAD'])[0].splitlines()[0]
   if current_branch != 'master':
     logging.error('Please checkout the master branch and re-run this script.')
     if not dry_run:
       sys.exit(-1)
 
+  logging.info('Updating master branch...')
+  _RunCommand(['git', 'pull'])

[pbos-webrtc, 2015/06/09 09:34:31]

Do you want to do this under a dry run? Also is there any sanity check possible
that you've not applied commits onto master?

[kjellander_webrtc, 2015/06/09 10:51:04]

I thought it shouldn't never hurt your checkout to run it, but sure, let's not
do it.
I added a check for a dirty tree, but I think it's hard to check that no local
commits have been made on master, let's skip that.

   logging.info('Creating roll branch: %s', ROLL_BRANCH_NAME)
   if not dry_run:
     _RunCommand(['git', 'checkout', '-b', ROLL_BRANCH_NAME])
 
 
 def _RemovePreviousRollBranch(dry_run):
   active_branch, branches = _GetBranches()
   if active_branch == ROLL_BRANCH_NAME:
     active_branch = 'master'
   if ROLL_BRANCH_NAME in branches:
@@ skipping 71 matching lines @@
   _CreateRollBranch(opts.dry_run)
   UpdateDeps(deps_filename, current_cr_rev, opts.revision)
   _LocalCommit(commit_msg, opts.dry_run)
   _UploadCL(opts.dry_run)
   _LaunchTrybots(opts.dry_run)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())