title: How to filter Github PRs that are merged and closed but the branch hasn't been deleted
body: <p>After submitting a PR in Github, it gets approved and then it's merged into master. At this point I should delete my branch to keep things tidy. I'm no angel and often forget to do this!</p>
  
  <p>Github has a handy Pull requests page to keep track of all your open/closed PRs. What I would like to know is, can a filter my PRs by the following:</p>
  
  <p><code>is:pr author:myusername is:closed is:merged</code> then something like <code>is:branchAliveYouFool</code></p>
  
  <p>This would show me all PRs that I've created, that are closed, that have been merged and, crucially, that haven't had the branch deleted.</p>
  
  <p>I've searched through the terms that can be used but can't find what I'm looking for:
  <a href="https://help.github.com/articles/searching-issues-and-pull-requests/" rel="noreferrer">https://help.github.com/articles/searching-issues-and-pull-requests/</a></p>
  
  <p>Any thoughts would be appreciated. Thanks :)</p>