title: git pull with "--work-tree" flag fails
body: <p>I'm running (in a script - trying to avoid using cd):</p>
  
  <pre><code>git --git-dir=/test/.git --work-tree=/test/ pull
  </code></pre>
  
  <p>And getting:</p>
  
  <pre><code>fatal: /usr/lib/git-core/git-pull cannot be used without a working tree.
  </code></pre>
  
  <p>Note that I've run other commands with exactly this structure that have worked (in particular, add, commit, and pull), so I think it's just a pull problem.</p>
  
  <p>A similar problem is documented here: <a href="https://stackoverflow.com/questions/7851967/git-pull-fails-to-parse-syntax">Git pull fails to parse syntax</a>, but it's not quite the same - they get a different error (and they're running on Windows, so who knows... I'm on Ubuntu).</p>