title: How do I selectively revert some changes in a single commit to a single file?
body: <p>My problem:  I stupidly made lots of changes to a file and committed them all at once.  </p>
  
  <p>I've since realized that much of the changes were crap ... but a lot of them were good, too.</p>
  
  <p>How do I selectively revert some portion of the changes?</p>