title: Cannot install `git-in-zsh` with zplug
body: <p>I am trying to install <code>git-in-zsh</code> with zplug but it didn't work at all. This is the line I used for getting the <code>.zsh</code> from <code>git/git</code></p>
  <pre class="lang-sh prettyprint-override"><code>zplug &quot;git/git&quot;, use:&quot;contrib/completion/*.zsh
  </code></pre>
  <p>The file I want to get is in this directory:</p>
  <p><a href="https://github.com/git/git/tree/master/contrib/completion" rel="nofollow noreferrer">https://github.com/git/git/tree/master/contrib/completion</a></p>
  <p>What have I done wrong with <code>zplug</code>? How can I source that file?</p>