docs: def diff(context, file_name):
      """See changes that occured since last check in"""
      context.obj.find_repo_type()
      if context.obj.vc_name == 'git':
          context.obj.call(['git', 'diff', '--color-words',
                            '--ignore-space-change', file_name])
      elif context.obj.vc_name == 'hg':
          context.obj.call(['hg', 'diff', file_name])