Fix the call to "git checkout" on Windows.

gclient_scm.py

 # Copyright (c) 2010 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 logging
 import os
 import posixpath
 import re
@@ skipping 295 matching lines @@
       print(remote_output.strip())
 
     # This is a big hammer, debatable if it should even be here...
     if options.force or options.reset:
       self._Run(['reset', '--hard', 'HEAD'], options)
 
     if current_type == 'detached':
       # case 0
       self._CheckClean(rev_str)
       self._CheckDetachedHead(rev_str, options)
-      self._Capture(['checkout', '--quiet', '%s^0' % revision])
+      self._Capture(['checkout', '--quiet', '%s' % revision])
       if not printed_path:
         print('\n_____ %s%s' % (self.relpath, rev_str))
     elif current_type == 'hash':
       # case 1
       if scm.GIT.IsGitSvn(self.checkout_path) and upstream_branch is not None:
         # Our git-svn branch (upstream_branch) is our upstream
         self._AttemptRebase(upstream_branch, files, options,
                             newbase=revision, printed_path=printed_path)
         printed_path = True
       else:
@@ skipping 184 matching lines @@
         # read". In the meantime, just make sure .git exists.
         if (e.args[0] == 'git command clone returned 128' and
             os.path.exists(os.path.join(self.checkout_path, '.git'))):
           print(str(e))
           print('Retrying...')
           continue
         raise e
 
     if detach_head:
       # Squelch git's very verbose detached HEAD warning and use our own
-      self._Capture(['checkout', '--quiet', '%s^0' % revision])
+      self._Capture(['checkout', '--quiet', '%s' % revision])
       print(
         ('Checked out %s to a detached HEAD. Before making any commits\n'
          'in this repo, you should use \'git checkout <branch>\' to switch to\n'
          'an existing branch or use \'git checkout origin -b <branch>\' to\n'
          'create a new branch for your work.') % revision)
 
   def _AttemptRebase(self, upstream, files, options, newbase=None,
                      branch=None, printed_path=False):
     """Attempt to rebase onto either upstream or, if specified, newbase."""
     files.extend(self._Capture(['diff', upstream, '--name-only']).split())
@@ skipping 405 matching lines @@
 
     This method returns a new list to be used as a command."""
     new_command = command[:]
     if revision:
       new_command.extend(['--revision', str(revision).strip()])
     # --force was added to 'svn update' in svn 1.5.
     if ((options.force or options.manually_grab_svn_rev) and
         scm.SVN.AssertVersion("1.5")[0]):
       new_command.append('--force')
     return new_command