title: Mercurial — revert back to old version and continue from there
body: <p>I'm using Mercurial locally for a project (it's the only repo there's no pushing/pulling to/from anywhere else).</p>
  
  <p>To date it's got a linear history.  However, the current thing I'm working on I've now realized is a terrible approach and I want to go back to the version before I started it and implement it a different way.</p>
  
  <p>I'm a bit confused with the <code>branch</code> / <code>revert</code> / <code>update -C</code> commands in Mercurial.  Basically I want to revert to version 38 (currently on 45) and have my next commits have 38 as a parent and carry on from there.  I don't care if revisions 39-45 are lost for ever or end up in a dead-end branch of their own.</p>
  
  <p>Which command / set of commands do I need?</p>