[release] Let release script fix missing tags.

tools/release/create_release.py

 #!/usr/bin/env python
 # Copyright 2015 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 os
 import sys
 import tempfile
 import urllib2
@@ skipping 205 matching lines @@
     if not text:  # pragma: no cover
       self.Die("Commit message editing failed.")
     self["commit_title"] = text.splitlines()[0]
     TextToFile(text, self.Config("COMMITMSG_FILE"))
 
     self.GitCommit(file_name = self.Config("COMMITMSG_FILE"))
     os.remove(self.Config("COMMITMSG_FILE"))
     os.remove(self.Config("CHANGELOG_ENTRY_FILE"))
 
 
+class FixBrokenTag(Step):
+  MESSAGE = "Check for a missing tag and fix that instead."
+
+  def RunStep(self):
+    commit = None
+    try:
+      commit = self.GitLog(
+          n=1, format="%H",
+          grep=self["commit_title"],
+          branch="origin/%s" % self["version"],
+      )
+    except GitFailedException:
+      # In the normal case, the remote doesn't exist yet and git will fail.
+      pass
+    if commit:
+      print "Found %s. Trying to repair tag and bail out." % self["version"]
+      self.step.Git("tag %s %s" % (self["version"], commit))
+      self.step.Git("push origin %s" % self["version"])
+      return True
+
+
 class PushBranch(Step):
   MESSAGE = "Push changes."
 
   def RunStep(self):
     pushspecs = [
       "refs/heads/work-branch:refs/pending/heads/%s" % self["version"],
       "%s:refs/pending-tags/heads/%s" % (self["push_hash"], self["version"]),
       "%s:refs/heads/%s" % (self["push_hash"], self["version"]),
     ]
     cmd = "push origin %s" % " ".join(pushspecs)
@@ skipping 60 matching lines @@
       PrepareBranchRevision,
       IncrementVersion,
       DetectLastRelease,
       PrepareChangeLog,
       EditChangeLog,
       MakeBranch,
       AddChangeLog,
       SetVersion,
       EnableMergeWatchlist,
       CommitBranch,
+      FixBrokenTag,
       PushBranch,
       TagRevision,
       CleanUp,
     ]
 
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(CreateRelease().Run())