title: How to `rebase` to avoid duplicated commits on pull request
body: <ol>
  <li>I did a PR to a repository. Accepted and merged.</li>
  <li><p>I <code>git fetch upstream</code> on my fork. </p>
  
  <p>[Here starts the stuff I could not understand at all]</p></li>
  <li><p>I have a <code>commit</code> with a pre compiled message: <em>Merge remote-tracking branch 'upstream/master'</em></p></li>
  <li><p>I pushed to my <code>remote</code></p></li>
  <li><p>Continue working on another feature, pushed to <code>remote</code> and create another <strong>Pull Request</strong> where have the (3) commits of the old PR, the <em>merge...</em> commit and the (2 last) commits that are relative to this feature.</p></li>
  </ol>
  
  <p><a href="https://github.com/pburtchaell/react-notification/pull/62" rel="nofollow noreferrer">Here</a> is the PR, where only the last two commits are necessary.</p>
  
  <p><a href="https://i.stack.imgur.com/JGCwf.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JGCwf.jpg" alt="desired commits"></a></p>
  
  <p>As you could see, the owner propose to <code>rebase</code> but, sincerely, don't know how to solve it the right way.</p>