title: <transition> can only be used on a single element
body: <pre><code>&lt;transition name="fade" mode="out-in"&gt;
    &lt;keep-alive&gt;
      &lt;router-view v-if="$route.meta.keepAlive"&gt;&lt;/router-view&gt;
    &lt;/keep-alive&gt;
    &lt;router-view v-if="!$route.meta.keepAlive"&gt;&lt;/router-view&gt;
  &lt;/transition&gt;
  </code></pre>
  
  <p>when i use the transition with keep-alive &amp; router-view, like above code, it will cause vue warn: <code>&lt;transition&gt;</code> can only be used on a single element.</p>
  
  <p>I know what caused the error, but I want to know how can i use the transition with keep-alive &amp; router-view correctly ?</p>