Add dry-run feature to auto roll scripts.

tools/push-to-trunk/auto_roll.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import json
 import os
 import sys
 import urllib
@@ skipping 82 matching lines @@
     if self._options.roll:
       args = [
         "--author", self._options.author,
         "--reviewer", self._options.reviewer,
         "--chromium", self._options.chromium,
         "--use-commit-queue",
       ]
       if self._options.sheriff:
         args.extend([
             "--sheriff", "--googlers-mapping", self._options.googlers_mapping])
+      if self._options.dry_run:
+        args.extend(["--dry-run"])
       R = chromium_roll.ChromiumRoll
       self._side_effect_handler.Call(
           R(chromium_roll.CONFIG, self._side_effect_handler).Run,
           args)
 
 
 class AutoRoll(ScriptsBase):
   def _PrepareOptions(self, parser):
     parser.add_argument("-c", "--chromium", required=True,
                         help=("The path to your Chromium src/ "
                               "directory to automate the V8 roll."))
-    parser.add_argument("--roll",
-                        help="Make Chromium roll. Dry run if unspecified.",
+    parser.add_argument("--roll", help="Call Chromium roll script.",
                         default=False, action="store_true")
 
   def _ProcessOptions(self, options):  # pragma: no cover
     if not options.reviewer:
       print "A reviewer (-r) is required."
       return False
     if not options.author:
       print "An author (-a) is required."
       return False
     return True
 
   def _Steps(self):
     return [
       CheckActiveRoll,
       DetectLastPush,
       DetectLastRoll,
       CheckClusterFuzz,
       RollChromium,
     ]
 
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(AutoRoll(CONFIG).Run())