Refactor git_common config and die

git_upstream_diff.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 import argparse
 import sys
 
 import subprocess2
 
 import git_common as git
 
 def main(args):
-  default_args = git.config_list('depot-tools.upstream-diff.default-args')
+  default_args = git.get_config_list('depot-tools.upstream-diff.default-args')
   args = default_args + args
 
   parser = argparse.ArgumentParser()
   parser.add_argument('--wordwise', action='store_true', default=False,
                       help=(
                         'Print a colorized wordwise diff '
                         'instead of line-wise diff'))
   opts, extra_args = parser.parse_known_args(args)
 
   cur = git.current_branch()
@@ skipping 15 matching lines @@
 
   return subprocess2.check_call(cmd)
 
 
 if __name__ == '__main__':
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)