[release-tools] Make chromium roll more robust after failing rolls.

tools/release/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 996 matching lines @@
       Cmd("git fetch origin", ""),
       Cmd("git fetch origin +refs/tags/*:refs/tags/*", ""),
       Cmd("git log -1 --format=%s roll_hsh",
           "Version 3.22.4 (based on abc)\n"),
       Cmd("git describe --tags roll_hsh", "3.22.4"),
       Cmd("git describe --tags last_roll_hsh", "3.22.2.1"),
       URL("https://chromium-build.appspot.com/p/chromium/sheriff_v8.js",
           "document.write('g_name')"),
       Cmd("git status -s -uno", "", cwd=chrome_dir),
       Cmd("git checkout -f master", "", cwd=chrome_dir),
+      Cmd("git branch", "", cwd=chrome_dir),
       Cmd("gclient sync --nohooks", "syncing...", cwd=chrome_dir),
       Cmd("git pull", "", cwd=chrome_dir),
       Cmd("git fetch origin", ""),
-      Cmd("git new-branch v8-roll-roll_hsh", "", cwd=chrome_dir),
+      Cmd("git new-branch work-branch", "", cwd=chrome_dir),
       Cmd("roll-dep v8 roll_hsh", "rolled", cb=WriteDeps, cwd=chrome_dir),
       Cmd(("git commit -am \"%s\" "
            "--author \"author@chromium.org <author@chromium.org>\"" %
            self.ROLL_COMMIT_MSG),
           "", cwd=chrome_dir),
       Cmd("git cl upload --send-mail --email \"author@chromium.org\" -f", "",
           cwd=chrome_dir),
+      Cmd("git checkout -f master", "", cwd=chrome_dir),
+      Cmd("git branch -D work-branch", "", cwd=chrome_dir),
     ]
     self.Expect(expectations)
 
     args = ["-a", "author@chromium.org", "-c", chrome_dir,
             "--sheriff",
             "-r", "reviewer@chromium.org",
             "--last-roll", "last_roll_hsh",
             "roll_hsh"]
     ChromiumRoll(TEST_CONFIG, self).Run(args)
 
@@ skipping 474 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)