Add --merge option to gclient sync.

gclient.py

 #!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Meta checkout manager supporting both Subversion and GIT.
 
 Files
   .gclient      : Current client configuration, written by 'config' command.
                   Format is a Python script defining 'solutions', a list whose
@@ skipping 1072 matching lines @@
   parser.add_option('-H', '--head', action='store_true',
                     help='skips any safesync_urls specified in '
                          'configured solutions and sync to head instead')
   parser.add_option('-D', '--delete_unversioned_trees', action='store_true',
                     help='delete any dependency that have been removed from '
                          'last sync as long as there is no local modification. '
                          'Coupled with --force, it will remove them even with '
                          'local modifications')
   parser.add_option('-R', '--reset', action='store_true',
                     help='resets any local changes before updating (git only)')
+  parser.add_option('-M', '--merge', action='store_true',
+                    help='merge upstream changes instead of trying to '
+                         'fast-forward or rebase')
   parser.add_option('--deps', dest='deps_os', metavar='OS_LIST',
                     help='override deps for the specified (comma-separated) '
                          'platform(s); \'all\' will process all deps_os '
                          'references')
   parser.add_option('-m', '--manually_grab_svn_rev', action='store_true',
                     help='Skip svn up whenever possible by requesting '
                          'actual HEAD revision from the repository')
   (options, args) = parser.parse_args(args)
   client = GClient.LoadCurrentConfig(options)
 
@@ skipping 199 matching lines @@
   except (gclient_utils.Error, subprocess2.CalledProcessError), e:
     print >> sys.stderr, 'Error: %s' % str(e)
     return 1
 
 
 if '__main__' == __name__:
   fix_encoding.fix_encoding()
   sys.exit(Main(sys.argv[1:]))
 
 # vim: ts=2:sw=2:tw=80:et: