title: Error while trying to update brew package manager
body: <p>I tried to update brew:</p>
  <pre><code>sudo brew update
  </code></pre>
  <p>But I got this error:</p>
  <blockquote>
  <p>error: Your local changes to the following files would be overwritten by merge:</p>
  <p>Listing a lot of files</p>
  <p>Error: Failed while executing git pull <a href="http://github.com/mxcl/homebrew.git" rel="noreferrer">http://github.com/mxcl/homebrew.git</a> master</p>
  </blockquote>
  <p>Any idea what is going wrong?</p>