docs: def tidy_ssh_user(url=None, user=None):
      """make sure a git repo ssh:// url has a user set"""
      if url and url.startswith('ssh://'):
          # is there a user already ?
          match = re.compile('ssh://([^@]+)@.+').match(url)
          if match:
              ssh_user = match.group(1)
              if user and ssh_user != user:
                  # assume prevalence of argument
                  url = url.replace(re.escape(ssh_user) + '@',
                                    user + '@')
          elif user:
              url = 'ssh://' + \
                    user + '@' + \
                    url[len('ssh://'):]
      return url