Add tag write access to merge script.

tools/push-to-trunk/push_to_trunk.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 267 matching lines @@
 
     # Remove indentation and merge paragraphs into single long lines, keeping
     # empty lines between them.
     def SplitMapJoin(split_text, fun, join_text):
       return lambda text: join_text.join(map(fun, text.split(split_text)))
     strip = lambda line: line.strip()
     text = SplitMapJoin("\n\n", SplitMapJoin("\n", strip, " "), "\n\n")(text)
 
     if not text:  # pragma: no cover
       self.Die("Commit message editing failed.")
+    self["commit_title"] = text.splitlines()[0]
     TextToFile(text, self.Config("COMMITMSG_FILE"))
 
 
 class NewBranch(Step):
   MESSAGE = "Create a new branch from trunk."
 
   def RunStep(self):
     self.GitCreateBranch(self.Config("TRUNKBRANCH"),
                          self.vc.RemoteCandidateBranch())
 
@@ skipping 56 matching lines @@
   MESSAGE = "Commit to SVN."
 
   def RunStep(self):
     result = self.vc.Land()
 
 
 class TagRevision(Step):
   MESSAGE = "Tag the new revision."
 
   def RunStep(self):
-    self.vc.Tag(self["version"], self.vc.RemoteCandidateBranch())
+    self.vc.Tag(
+        self["version"], self.vc.RemoteCandidateBranch(), self["commit_title"])
 
 
 class CleanUp(Step):
   MESSAGE = "Done!"
 
   def RunStep(self):
     print("Congratulations, you have successfully created the trunk "
           "revision %s."
           % self["version"])
 
@@ skipping 65 matching lines @@
       CommitTrunk,
       SanityCheck,
       CommitSVN,
       TagRevision,
       CleanUp,
     ]
 
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(PushToTrunk().Run())