code: def refresh(cls):
          
          # clear the old values in _flag_map
          try:
              del cls._flag_map["t"]
          except KeyError:
              pass
  
          try:
              del cls._flag_map["-"]
          except KeyError:
              pass
  
          # set the value given the git version
          if Git().version_info[:2] >= (2, 10):
              cls._flag_map["t"] = cls.TAG_UPDATE
          else:
              cls._flag_map["-"] = cls.TAG_UPDATE
  
          return True
docs: This gets called by the refresh function (see the top level
          __init__).