title: How do I copy a version of a single file from one Git branch to another?
body: <p>I've got two branches that are fully merged together.</p>
  <p>However, after the merge is done, I realise that one file has been messed up by the merge (someone else did an auto-format, gah), and it would just be easier to change to the new version in the other branch, and then reinsert my one line change after bringing it over into my branch.</p>
  <p>So what's the easiest way in Git to do this?</p>