fatal: Invalid refspec '+refs/heads/*'
<p>In <a href="https://www.kernel.org/pub/software/scm/git/docs/git-fetch.html" rel="nofollow">git-fetch</a> doc, you can see:</p>

<blockquote>
  <p>The remote ref that matches &lt;src&gt; is fetched, and if &lt;dst&gt; is not
  <strong><em>empty string</em></strong>, the local ref that matches it is fast-forwarded using
  &lt;src&gt;. If the optional plus + is used, the local ref is updated even
  if it does not result in a fast-forward update.</p>
</blockquote>

<p>So we can use <code>empty string as destination</code>. Now my current repository has a remote which it's name is <code>origin</code>. When I try to fetch like this, I get an error:</p>

<pre><code>git fetch origin +refs/heads/*
fatal: Invalid refspec '+refs/heads/*'
</code></pre>

<p>But why an <code>empty string</code> cause <code>invalid refspec</code>?</p>