Allow --3way to be passed to `git apply` via `git cl patch`.

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 1675 matching lines @@
 
 @usage('<patch url or issue id>')
 def CMDpatch(parser, args):
   """patch in a code review"""
   parser.add_option('-b', dest='newbranch',
                     help='create a new branch off trunk for the patch')
   parser.add_option('-f', action='store_true', dest='force',
                     help='with -b, clobber any existing branch')
   parser.add_option('--reject', action='store_true', dest='reject',
                     help='allow failed patches and spew .rej files')
+  parser.add_option('-3', '--3way', action='store_true', dest='three_way',
+                    help='allow failed patches to fall back on 3-way merge, '
+                        'possibly leaving conflict markers to resolve')
   parser.add_option('-n', '--no-commit', action='store_true', dest='nocommit',
                     help="don't commit after patch applies")
   (options, args) = parser.parse_args(args)
   if len(args) != 1:
     parser.print_help()
     return 1
   issue_arg = args[0]
 
   # TODO(maruel): Use apply_issue.py
   # TODO(ukai): use gerrit-cherry-pick for gerrit repository?
@@ skipping 37 matching lines @@
         ['sed', '-e', 's|^--- a/|--- |; s|^+++ b/|+++ |'], stdin=patch_data)
   except subprocess2.CalledProcessError:
     DieWithError('Git patch mungling failed.')
   logging.info(patch_data)
   # We use "git apply" to apply the patch instead of "patch" so that we can
   # pick up file adds.
   # The --index flag means: also insert into the index (so we catch adds).
   cmd = ['git', '--no-pager', 'apply', '--index', '-p0']
   if options.reject:
     cmd.append('--reject')
+  elif options.three_way:

[M-A Ruel, 2013/06/05 18:47:34]

I'm fine with adding it as the default without an option to disable it. The tool
should return 1 if there is a merge conflict though. Please test it so that git
cl doesn't stack trace here in that case.

+    cmd.append('--3way')
   try:
     subprocess2.check_call(cmd, stdin=patch_data, stdout=subprocess2.VOID)
   except subprocess2.CalledProcessError:
     DieWithError('Failed to apply the patch')
 
   # If we had an issue, commit the current state and register the issue.
   if not options.nocommit:
     RunGit(['commit', '-m', 'patch from issue %s' % issue])
     cl = Changelist()
     cl.SetIssue(issue)
@@ skipping 330 matching lines @@
   GenUsage(parser, 'help')
   return CMDhelp(parser, argv)
 
 
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   sys.exit(main(sys.argv[1:]))