title: How to git fetch and checkout without creating a remote branch locally?
body: <p>Use Case: I have some repo on GitHub, someone forked it and added new feature and initiated pull request. 
  I can't automatically merge it because there are some minor problems I would like to fix first. </p>
  
  <p>It's one-time activity I'll never need this remote repository, so I don't want to create local <code>remote</code> branch.</p>
  
  <p>Basically I would like to do:</p>
  
  <ol>
  <li>copy files from remote repository and rewrite my own (without any git-related information).</li>
  <li>see difference with my current head.</li>
  <li>fix something and commit it.</li>
  </ol>
  
  <p>How to do that?</p>
  
  <p><code>git checkout git://github.com/xxx/xxx.git</code> doesn't works at all (fail with error)</p>
  
  <p><code>git fetch git://github.com/xxx/xxx.git</code> works but doesn't update anything</p>