title: hgignore: help ignoring all files but certain ones
body: <p>I need an .hgdontignore file :-) to include certain files and exclude everything else in a directory. Basically I want to include only the .jar files in a particular directory and nothing else. How can I do this? I'm not that skilled in regular expression syntax. Or can I do it with glob syntax? (I prefer that for readability)</p>
  
  <p>Just as an example location, let's say I want to exclude all files under <code>foo/bar/</code> except for <code>foo/bar/*.jar</code>.</p>