code: def register(cls, name, description, options_registrar_cls=None):
      
      goal = cls.by_name(name)
      goal._description = description
      goal._options_registrar_cls = (options_registrar_cls.registrar_for_scope(name)
                                     if options_registrar_cls else None)
      return goal
docs: Register a goal description.
  
      Otherwise the description must be set when registering some task on the goal,
      which is clunky, and dependent on things like registration order of tasks in the goal.
  
      A goal that isn't explicitly registered with a description will fall back to the description
      of the task in that goal with the same name (if any).  So singleton goals (e.g., 'clean-all')
      need not be registered explicitly.  This method is primarily useful for setting a
      description on a generic goal like 'compile' or 'test', that multiple backends will
      register tasks on.
  
      :API: public
  
      :param string name: The name of the goal; ie: the way to specify it on the command line.
      :param string description: A description of the tasks in the goal do.
      :param :class:pants.option.Optionable options_registrar_cls: A class for registering options
             at the goal scope. Useful for registering recursive options on all tasks in a goal.
      :return: The freshly registered goal.
      :rtype: :class:`_Goal`