title: Undo git push mirror
body: <p>I have a server with my project.
  I wanted to migrate to github.
  I did a push --mirror to github.
  I checked if backup could be done in reverse
  So I did a push --mirror to my server.
  But here is what I get:</p>
  
  <pre><code>To &lt;adresse.git&gt;
   + 1e35d97...3ef6b80 master -&gt; master (forced update)
     c46a188..3ef6b80  origin/HEAD -&gt; origin/HEAD
     c46a188..3ef6b80  origin/master -&gt; origin/master
   - [deleted]         1.0.0
   - [deleted]         1.0.1
   - [deleted]         1.0.2
   - [deleted]         1.0.3
   - [deleted]         1.0.4
   - [deleted]         1.0.5
   - [deleted]         1.1.0
   - [deleted]         1.1.1
   - [deleted]         1.2.0
   - [deleted]         1.2.1
   - [deleted]         1.2_alpha1
   - [deleted]         1.3_alpha1
   - [deleted]         1.4_alpha1
   - [deleted]         4.0.0
   - [deleted]         5.0.0
   - [deleted]         5.0.1
   - [deleted]         xvp_current
  </code></pre>
  
  <p>I didn't noticed (Ooooh mistake..) and did a last push --mirror from my server to github this morning which conclude by the last same output..
  Those are my releases. Is there any way to cancel mirror or to get back the releases ?</p>
  
  <p>Thanks in advance!</p>