code: func (a *ActivateExecution) RollForward(c context.Context) (muts []tumble.Mutation, err error) {
  	_, e, err := model.ActivateExecution(c, a.Auth, a.NewTok)
  	if err == nil {
  		err = ResetExecutionTimeout(c, e)
  	}
  	return
  }
docs: // RollForward implements tumble.Mutation