title: How to include only specific directories in rdoc?
body: <p>I'm using <code>rdoc</code> to generate API documentation for my Ruby program, but it's pulling in lots of files I don't care to include in the documentation. I see that there is an option to exclude files by pattern, but it would really be better for me to simply provide an explicit list of files and directories to include.</p>
  <p>Is there an option to do this, or am I out of luck?</p>