title: git equivalent for hg rollback
body: <p>How would I "rollback" the last commit in git without deleting any changes?</p>
  
  <p>This is something I've done often in hg:</p>
  
  <ul>
  <li>Commit "Fixed 107."</li>
  <li>Remembered that I forgot to do <em>something</em></li>
  <li>hg rollback</li>
  <li>Do <em>something</em></li>
  <li>Commit "Fixed 107."</li>
  </ul>