docs: def get_rev_options(url, rev):
      """Return revision options.
  
      from pip pip.vcs.subversion.
  
      """
      if rev:
          rev_options = ['-r', rev]
      else:
          rev_options = []
  
      r = urlparse.urlsplit(url)
      if hasattr(r, 'username'):
          # >= Python-2.5
          username, password = r.username, r.password
      else:
          netloc = r[1]
          if '@' in netloc:
              auth = netloc.split('@')[0]
              if ':' in auth:
                  username, password = auth.split(':', 1)
              else:
                  username, password = auth, None
          else:
              username, password = None, None
  
      if username:
          rev_options += ['--username', username]
      if password:
          rev_options += ['--password', password]
      return rev_options