title: Git sparse checkout with exclusion
body: <p>According to <a href="http://git.661346.n2.nabble.com/git-sparse-checkout-exclusions-not-working-td6310207.html" rel="noreferrer">this thread</a>, exclusion in Git's <a href="https://stackoverflow.com/q/2336580/946850"><code>sparse-checkout</code> feature</a> is supposed to be implemented.  Is it?</p>
  
  <p>Assume that I have the following structure:</p>
  
  <pre><code>papers/
  papers/...
  presentations/
  presentations/heavy_presentation
  presentations/...
  </code></pre>
  
  <p>Now I want to exclude <code>presentations/heavy_presentation</code> from the checkout, while leaving the rest in the checkout. I haven't managed to get this running. What's the right syntax for this?</p>