Fix maintaining change log in push-to-trunk.

tools/push-to-trunk/test_scripts.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 723 matching lines @@
       Git("svn fetch", "fetch result\n"),
       Git("checkout -f svn/bleeding_edge", ""),
       Git(("log -1 --format=%H --grep=\"Prepare push to trunk.  "
            "Now working on version 3.22.6.\""),
           "hash1\n"),
       Git("diff svn/trunk hash1", "patch content\n"),
       Git("svn find-rev hash1", "123455\n"),
       Git("checkout -b %s svn/trunk" % TEST_CONFIG[TRUNKBRANCH], "",
           cb=ResetChangeLog),
       Git("apply --index --reject \"%s\"" % TEST_CONFIG[PATCH_FILE], ""),
-      Git("checkout -- %s" % TEST_CONFIG[CHANGELOG_FILE], "",
+      Git("checkout -f -- %s" % TEST_CONFIG[CHANGELOG_FILE], "",
           cb=ResetChangeLog),
       Git("add \"%s\"" % TEST_CONFIG[VERSION_FILE], ""),
       Git("commit -aF \"%s\"" % TEST_CONFIG[COMMITMSG_FILE], "",
           cb=CheckSVNCommit),
       Git("svn dcommit 2>&1", "Some output\nCommitted r123456\nSome output\n"),
       Git("svn tag 3.22.5 -m \"Tagging version 3.22.5\"", ""),
       Git("status -s -uno", ""),
       Git("checkout -f master", ""),
       Git("pull", ""),
       Git("checkout -b v8-roll-123456", ""),
@@ skipping 287 matching lines @@
 
 Review URL: https://codereview.chromium.org/83173002
 
 ------------------------------------------------------------------------""")
     self.assertEquals(
 """Prepare push to trunk.  Now working on version 3.23.11.
 
 R=danno@chromium.org
 
 Committed: https://code.google.com/p/v8/source/detail?r=17997""", body)