Fix resolution of local branch name in scm and rebaseline tools.

Tools/Scripts/webkitpy/tool/commands/rebaseline.py

 # Copyright (c) 2010 Google Inc. 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 disclaimer
@@ skipping 39 matching lines @@
 
 
 _log = logging.getLogger(__name__)
 
 
 # FIXME: Should TestResultWriter know how to compute this string?
 def _baseline_name(fs, test_name, suffix):
     return fs.splitext(test_name)[0] + TestResultWriter.FILENAME_SUFFIX_EXPECTED + "." + suffix
 
 
+def _get_branch_name_or_ref(tool):
+    branch_name = tool.scm().current_branch()
+    if not branch_name:
+        # If HEAD is detached use commit SHA instead.
+        return tool.executive.run_command(['git', 'rev-parse', 'HEAD']).strip()
+    return branch_name
+
+
 class AbstractRebaseliningCommand(AbstractDeclarativeCommand):
     # not overriding execute() - pylint: disable=W0223
 
     no_optimize_option = optparse.make_option('--no-optimize', dest='optimize', action='store_false', default=True,
         help=('Do not optimize/de-dup the expectations after rebaselining (default is to de-dup automatically). '
               'You can use "webkit-patch optimize-baselines" to optimize separately.'))
 
     platform_options = factory.platform_options(use_globs=True)
 
     results_directory_option = optparse.make_option("--results-directory", help="Local results directory to use")
@@ skipping 757 matching lines @@
 
         if self.tree_status() == 'closed':
             _log.info('Cannot proceed. Tree is closed.')
             return
 
         _log.info('Rebaselining %s for r%s by %s.' % (list(tests), revision, author))
 
         test_prefix_list, lines_to_remove = self.get_test_prefix_list(tests)
 
         did_finish = False
+        old_branch_name_or_ref = ''
         try:
             # Setup git-svn for dcommit if necessary.
             if tool.executive.run_command(
                     ['git', 'config', '--local', '--get-regexp', r'^svn-remote\.'],
                     return_exit_code=True):
                 tool.executive.run_command(['git', 'auto-svn'])
 
             # Save the current branch name and checkout a clean branch for the patch.
-            old_branch_name = tool.executive.run_command(
-                ["git", "rev-parse", "--symbolic-full-name", "HEAD"])
-            if old_branch_name == "HEAD":
-                # If HEAD is detached use commit SHA instead.
-                old_branch_name = tool.executive.run_command(["git", "rev-parse", "HEAD"])
+            old_branch_name_or_ref = _get_branch_name_or_ref(tool)
             tool.scm().delete_branch(self.AUTO_REBASELINE_BRANCH_NAME)
             tool.scm().create_clean_branch(self.AUTO_REBASELINE_BRANCH_NAME)
 
             # If the tests are passing everywhere, then this list will be empty. We don't need
             # to rebaseline, but we'll still need to update TestExpectations.
             if test_prefix_list:
                 self._rebaseline(options, test_prefix_list)
 
             tool.scm().commit_locally_with_message(self.commit_message(author, revision, bugs))
 
@@ skipping 14 matching lines @@
             traceback.print_exc(file=sys.stderr)
         finally:
             if did_finish:
                 # Close the issue if dcommit failed.
                 issue = tool.executive.run_command(
                     ['git', 'config', 'branch.%s.rietveldissue' % self.AUTO_REBASELINE_BRANCH_NAME])
                 if issue.strip():
                     self._run_git_cl_command(options, ['set_close'])
 
             tool.scm().ensure_cleanly_tracking_remote_master()
-            tool.scm().checkout_branch(old_branch_name)
+            if old_branch_name_or_ref:
+                tool.scm().checkout_branch(old_branch_name_or_ref)
             tool.scm().delete_branch(self.AUTO_REBASELINE_BRANCH_NAME)
 
 
 class RebaselineOMatic(AbstractDeclarativeCommand):
     name = "rebaseline-o-matic"
     help_text = "Calls webkit-patch auto-rebaseline in a loop."
     show_in_main_help = True
 
     SLEEP_TIME_IN_SECONDS = 30
     LOG_SERVER = 'blinkrebaseline.appspot.com'
@@ skipping 40 matching lines @@
 
         out = self._log_line(process.stdout)
         while out:
             # FIXME: This should probably batch up lines if they're available and log to the server once.
             out = self._log_line(process.stdout)
 
     def _do_one_rebaseline(self):
         self._log_queue = Queue.Queue(256)
         log_thread = threading.Thread(name='LogToServer', target=self._log_to_server_thread)
         log_thread.start()
+        old_branch_name_or_ref = ''
         try:
-            old_branch_name = self._tool.scm().current_branch()
+            old_branch_name_or_ref = _get_branch_name_or_ref(self._tool)
             self._run_logged_command(['git', 'pull'])
             rebaseline_command = [self._tool.filesystem.join(self._tool.scm().checkout_root, 'Tools', 'Scripts', 'webkit-patch'), 'auto-rebaseline']
             if self._verbose:
                 rebaseline_command.append('--verbose')
             self._run_logged_command(rebaseline_command)
         except:
             self._log_queue.put(self.QUIT_LOG)
             traceback.print_exc(file=sys.stderr)
             # Sometimes git crashes and leaves us on a detached head.
-            self._tool.scm().checkout_branch(old_branch_name)
+            if old_branch_name_or_ref:
+                self._tool.scm().checkout_branch(old_branch_name_or_ref)
         else:
             self._log_queue.put(self.QUIT_LOG)
         log_thread.join()
 
     def execute(self, options, args, tool):
         self._verbose = options.verbose
         while True:
             self._do_one_rebaseline()
             time.sleep(self.SLEEP_TIME_IN_SECONDS)