Fix typo in merge script.

tools/release/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 321 matching lines @@
     return "origin/candidates"
 
   def RemoteBranch(self, name):
     # Assume that if someone "fully qualified" the ref, they know what they
     # want.
     if name.startswith('refs/'):
       return name
     if name in ["candidates", "master"]:
       return "refs/remotes/origin/%s" % name
     # Check if branch is in heads.
-    if self.Git("show-ref refs/remotes/origin/%s" % name).strip():
+    if self.step.Git("show-ref refs/remotes/origin/%s" % name).strip():
       return "refs/remotes/origin/%s" % name
     # Check if branch is in branch-heads.
-    if self.Git("show-ref refs/remotes/branch-heads/%s" % name).strip():
+    if self.step.Git("show-ref refs/remotes/branch-heads/%s" % name).strip():
       return "refs/remotes/branch-heads/%s" % name
     self.Die("Can't find remote of %s" % name)
 
   def Tag(self, tag, remote, message):
     # Wait for the commit to appear. Assumes unique commit message titles (this
     # is the case for all automated merge and push commits - also no title is
     # the prefix of another title).
     commit = None
     for wait_interval in [3, 7, 15, 35, 45, 60]:
       self.step.Git("fetch")
@@ skipping 527 matching lines @@
     for (number, step_class) in enumerate([BootstrapStep] + 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 0
     return 0
 
   def Run(self, args=None):
     return self.RunSteps(self._Steps(), args)