Add dry-run feature to auto roll scripts.

tools/push-to-trunk/common_includes.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 574 matching lines @@
   def _ProcessOptions(self, options):
     return True
 
   def _Steps(self):  # pragma: no cover
     raise Exception("Not implemented.")
 
   def MakeOptions(self, args=None):
     parser = argparse.ArgumentParser(description=self._Description())
     parser.add_argument("-a", "--author", default="",
                         help="The author email used for rietveld.")
+    parser.add_argument("--dry-run", default=False, action="store_true",
+                        help="Perform only read-only actions.")
     parser.add_argument("-g", "--googlers-mapping",
                         help="Path to the script mapping google accounts.")
     parser.add_argument("-r", "--reviewer", default="",
                         help="The account name to be used for reviews.")
     parser.add_argument("--sheriff", default=False, action="store_true",
                         help=("Determine current sheriff to review CLs. On "
                               "success, this will overwrite the reviewer "
                               "option."))
     parser.add_argument("-s", "--step",
         help="Specify the step where to start work. Default: 0.",
@@ skipping 45 matching lines @@
     for (number, step_class) in enumerate(step_classes):
       steps.append(MakeStep(step_class, number, self._state, self._config,
                             options, self._side_effect_handler))
     for step in steps[options.step:]:
       if step.Run():
         return 1
     return 0
 
   def Run(self, args=None):
     return self.RunSteps(self._Steps(), args)