title: Is HEAD in git case insensitive on all platforms?
body: <p>Using msysgit on Windows, I can do this:</p>
  
  <pre><code>git checkout head
  </code></pre>
  
  <p>or</p>
  
  <pre><code>git checkout HEAD
  </code></pre>
  
  <p>Either works. I don't have a linux environment to test on, but I'm just curious: is <code>HEAD</code> case insensitive by design? Is it this way on all platforms?</p>