Add fully automated mode to push-to-trunk script.

tools/push-to-trunk/auto_roll.py

 #!/usr/bin/env python
 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
@@ skipping 78 matching lines @@
     Preparation,
     FetchLatestRevision,
     FetchLKGR,
     PushToTrunk,
   ]
   RunScript(step_classes, config, options, side_effect_handler)
 
 
 def BuildOptions():
   result = optparse.OptionParser()
+  result.add_option("-f", "--force", dest="f",
+                    help="Don't prompt the user.",
+                    default=True, action="store_true")
   result.add_option("-s", "--step", dest="s",
                     help="Specify the step where to start work. Default: 0.",
                     default=0, type="int")
   return result
 
 
 def Main():
   parser = BuildOptions()
   (options, args) = parser.parse_args()
   RunAutoRoll(CONFIG, options)
 
 if __name__ == "__main__":
   sys.exit(Main())