Make git-try --webkit work like it used to work.

trychange.py

 #!/usr/bin/python
 # Copyright (c) 2009 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.
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 """
 
 import datetime
@@ skipping 494 matching lines @@
                         "patch created in a subdirectory")
   group.add_option("-p", "--patchlevel", type='int', metavar="LEVEL",
                    help="Used as -pN parameter to patch")
   group.add_option("-s", "--sub_rep", action="append", default=[],
                    help="Subcheckout to use in addition. This is mainly "
                         "useful for gclient-style checkouts. Use @rev or "
                         "@branch or @branch1..branch2 to specify the "
                         "revision/branch to diff against.")
   # Mostly chromium-specific
   try:
-    group.add_option("--webkit", action="append_const",
-                     const="third_party/WebKit",
-                     dest="PATH",
-                     help="Shorthand for -s third_party/WebKit")
+    def WebKitRevision(options, opt, value, parser):
+      if parser.rargs and not parser.rargs[0].startswith('-'):
+        options.sub_rep.append('third_party/WebKit@%s' % parser.rargs.pop(0))
+      else:
+        options.sub_rep.append('third_party/WebKit')
+
+    group.add_option("-W", "--webkit", action="callback",
+                     callback=WebKitRevision,
+                     metavar="BRANCH",
+                     help="Shorthand for -s third_party/WebKit@BRANCH. "
+                          "BRANCH is optional and is the branch the current "
+                          "checkout will be diff'ed against.")
   except optparse.OptionError:
     # append_const is not supported on 2.4. Too bad.
     pass
   group.add_option("--no_gclient", action="store_true",
                    help="Disable automatic search for gclient checkout.")
   group.add_option("-E", "--exclude", action="append",
                    default=['ChangeLog'], metavar='REGEXP',
                    help="Regexp patterns to exclude files. Default: %default")
   parser.add_option_group(group)
 
@@ skipping 155 matching lines @@
   except (InvalidScript, NoTryServerAccess), e:
     if swallow_exception:
       return 1
     print e
     return 1
   return 0
 
 
 if __name__ == "__main__":
   sys.exit(TryChange(None, [], False))