title: Github: Clean up fork after pull request
body: <p>I have forked a github repository, made a commit (title <code>Some small changes</code>), submitted a pull request and it got merged into the main repository (commit title <code>Some small changes (#12)</code>, where <code>#12</code> is the pull request number). So far, so good.</p>
  
  <p>Now, when I want to update my fork (<code>git rebase upstream/master</code>, see <a href="https://stackoverflow.com/questions/7244321/how-do-i-update-a-github-forked-repository">here</a>), I have this commit twice in my repository. First as <code>Some small changes</code> and then again as <code>Some small changes (#12)</code>. If I create a new pull request, the <code>Some small changes</code> commit is again added to the pull request.</p>
  
  <p>There are two ways to work around this issue:</p>
  
  <ol>
  <li>Clean up my fork, see <a href="https://stackoverflow.com/a/9646323/4920424">this answer</a></li>
  <li>Merge all commits into one, see <a href="https://stackoverflow.com/a/6103022/4920424">this answer</a></li>
  </ol>
  
  <p>Both cases involve rewriting my history and having to force-push. Is there a better way to keep your fork in sync while committing pull requests?</p>