Fix hook disable logic in gclient_scm (non-atomic os.rename on Windows)

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."""
 
 from __future__ import print_function
 
 import errno
 import logging
@@ skipping 300 matching lines @@
     if file_list is not None:
       files = self._Capture(['ls-files']).splitlines()
       file_list.extend([os.path.join(self.checkout_path, f) for f in files])
 
   def _DisableHooks(self):
     hook_dir = os.path.join(self.checkout_path, '.git', 'hooks')
     if not os.path.isdir(hook_dir):
       return
     for f in os.listdir(hook_dir):
       if not f.endswith('.sample') and not f.endswith('.disabled'):
-        os.rename(os.path.join(hook_dir, f),
-                  os.path.join(hook_dir, f + '.disabled'))
+        disabled_hook_path = os.path.join(hook_dir, f + '.disabled')
+        if os.path.exists(disabled_hook_path):
+          os.remove(disabled_hook_path)
+        os.rename(os.path.join(hook_dir, f), disabled_hook_path)
 
   def update(self, options, args, file_list):
     """Runs git to update or transparently checkout the working copy.
 
     All updated files will be appended to file_list.
 
     Raises:
       Error: if can't get URL for relative path.
     """
     if args:
@@ skipping 1290 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