title: How can I make the current (non HEAD) revision the only HEAD of my branch
body: <p>I have:</p>
  
  <ol>
  <li>Created a branch off a wrong branch and did some work</li>
  <li>Created the branch off the correct branch, ending up with 2 HEADS</li>
  <li>Did some work, merged them, only to realise I don't want one of the HEADS at all and want to go back to make an earlier revision the only HEAD.</li>
  </ol>
  
  <p><a href="https://i.stack.imgur.com/gjzii.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gjzii.png" alt="I want this to be the head"></a></p>
  
  <p>How can I make my current revision (<code>mid 236</code>) the only HEAD of my branch in Mercurial?</p>