Fix some path processing to work better on Windows.

cit.py

 #!/usr/bin/env python
 # Copyright (c) 2015 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.
 
 
 """Wrapper for updating and calling infra.git tools.
 
 This tool does a two things:
 * Maintains a infra.git checkout pinned at "deployed" in the home dir
 * Acts as an alias to infra.tools.*
 """
 
 # TODO(hinoka): Use cipd/glyco instead of git/gclient.
 
 import argparse
 import sys
 import os
 import subprocess
 import re
 
 
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
 GCLIENT = os.path.join(SCRIPT_DIR, 'gclient.py')
-TARGET_DIR = os.path.expanduser('~/.chrome-infra')
+TARGET_DIR = os.path.expanduser(os.path.join('~', '.chrome-infra'))
 INFRA_DIR = os.path.join(TARGET_DIR, 'infra')
 
 
 def get_git_rev(target, branch):
   return subprocess.check_output(
       ['git', 'log', '--format=%B', '-n1', branch], cwd=target)
 
 
 def need_to_update(branch):
   """Checks to see if we need to update the ~/.chrome-infra/infra checkout."""
@@ skipping 75 matching lines @@
     args.args.pop(0)
   if extras:
     args.args = extras + args.args
 
   if need_to_update(args.infra_branch):
     ensure_infra(args.infra_branch)
   return run(args.args)
 
 if __name__ == '__main__':
   sys.exit(main())