title: How to undo all added files in Mercurial
body: <p>Say I type <code>hg add</code> in Mercurial, and there a bunch of untracked files in my working directory that are not ignored. What is the easiest way to un-add all those files without explicitly typing the name of each file?</p>
  
  <p>Can I just un-add them all with one command? </p>