title: Undoing a 'git push'
body: <p>Here's what I did on my <em>supposed-to-be-stable</em> branch...</p>
  
  <pre class="lang-bash prettyprint-override"><code>% git rebase master
  First, rewinding head to replay your work on top of it...
  Fast-forwarded alpha-0.3.0 to master.
  % git status
  # On branch alpha-0.3.0
  # Your branch is ahead of 'origin/alpha-0.3.0' by 53 commits.
  #
  nothing to commit (working directory clean)
  % git push
  Fetching remote heads...
    refs/
    refs/heads/
    refs/tags/
    refs/remotes/
  'refs/heads/master': up-to-date
  updating 'refs/heads/alpha-0.3.0'
    from cc4b63bebb6e6dd04407f8788938244b78c50285
    to   83c9191dea88d146400853af5eb7555f252001b0
      done
  'refs/heads/unstable': up-to-date
  Updating remote server info
  </code></pre>
  
  <p>That was all a mistake as I later realized. I'd like to undo this entire process, and revert the alpha-0.3.0 branch back to what it was.</p>
  
  <p>What should I do?</p>