title: How do I check out a specific commit from Github?
body: <p>I'm trying to checkout <code>https://github.com/Miserlou/Zappa/commit/54a6fa4542a4ae26d5a8155b63a50701ab69c1f8</code>.</p>
  
  <pre><code>$ git clone https://github.com/Miserlou/Zappa.git
  Cloning into 'Zappa'...
  remote: Enumerating objects: 15029, done.
  remote: Total 15029 (delta 0), reused 0 (delta 0), pack-reused 15029
  Receiving objects: 100% (15029/15029), 4.71 MiB | 932.00 KiB/s, done.
  Resolving deltas: 100% (11418/11418), done.
  $ cd Zappa
  $ git checkout 54a6fa4542a4ae26d5a8155b63a50701ab69c1f8
  fatal: reference is not a tree: 54a6fa4542a4ae26d5a8155b63a50701ab69c1f8
  </code></pre>
  
  <p>What am I doing wrong?</p>