Don't allow 'detached head' branch creation to fail.

gclient_scm.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Gclient-specific SCM-specific operations."""
 
 import collections
 import logging
 import os
 import posixpath
@@ skipping 1000 matching lines @@
         # Punt to the user
         raise gclient_utils.Error('\n____ %s%s\n'
                                   '\tAlready in a conflict, i.e. (no branch).\n'
                                   '\tFix the conflict and run gclient again.\n'
                                   '\tOr to abort run:\n\t\tgit-rebase --abort\n'
                                   '\tSee man git-rebase for details.\n'
                                    % (self.relpath, rev_str))
       # Let's just save off the commit so we can proceed.
       name = ('saved-by-gclient-' +
               self._Capture(['rev-parse', '--short', 'HEAD']))
-      self._Capture(['branch', name])
+      self._Capture(['branch', '-f', name])
       print('\n_____ found an unreferenced commit and saved it as \'%s\'' %
           name)
 
   def _GetCurrentBranch(self):
     # Returns name of current branch or None for detached HEAD
     branch = self._Capture(['rev-parse', '--abbrev-ref=strict', 'HEAD'])
     if branch == 'HEAD':
       return None
     return branch
 
@@ skipping 442 matching lines @@
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'theirs-conflict'))
     elif options.manually_grab_svn_rev:
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'postpone'))
     elif command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
       new_command.extend(('--accept', 'postpone'))
     return new_command