Ember.js 使用pushObject后如何回滚未限制的关系？

给定一个

标签

和

post

多个关系，定义如下：

post.js

tag.js

使用

pushObject将
标记添加到
post
时

let aPost = this.store.findRecord('post', 1),
    aTag  = this.store.findRecord('tag', 1);

aPost.get('tags').pushObject(aTag); // aPost is not commited yet

如何将标签恢复到初始状态

import Ember from 'ember';
import Model from 'ember-data/model';
import { hasMany } from 'ember-data/relationships';

export default Model.extend({
  posts: hasMany('post')
}

let aPost = this.store.findRecord('post', 1),
    aTag  = this.store.findRecord('tag', 1);

aPost.get('tags').pushObject(aTag); // aPost is not commited yet