title: What does git "updating currently checked out branch" warning mean?
body: <p>When I do a git push, I see the following:</p>
  
  <pre><code>warning: updating the currently checked out branch; this may cause confusion,
  as the index and working tree do not reflect changes that are now in HEAD.
  </code></pre>
  
  <p>I Googled for this message, and all I can find is a <a href="http://article.gmane.org/gmane.comp.version-control.git/107814" rel="noreferrer">git mailing list discussion</a> where the authors try to decide exactly how to make this message better to communicate to me what the real problem is.</p>
  
  <p>How did I cause this, and how do I fix it?</p>