title: Is there a way to squash a commits in already merged pull request?
body: <p>Consider this scenario:</p>
  
  <ol>
  <li>I am working on my local feature or defect branch which is created
  from develop branch. </li>
  <li>Then I released my changes as multiple commits
  to my remote branch (as it happens in the PR review process). </li>
  <li>My PR is finally approved by team reviewing my changes. But I forgot to
  quash all my commits on my remote and local branch and merged my
  remote branch in to develop branch.</li>
  <li>Deleted the local and remote branch.</li>
  </ol>
  
  <p>Now I realized that I merged my changes in to develop without doing a squash. </p>
  
  <p><strong>So is there way for me to squash my commits in to develop branch after the fact that all my commits were merged in develop branch ?</strong></p>