title: Syntax coloring within diffs?
body: <p>In emacs, when I diff code I lose the syntax highlighting. With my theme anyway all text is light gray. Added lines do have a green background, and removed lines do have a red background, etc. But the code keywords, etc are not colored like they are when I'm using that language's mode. Is there a way to turn on ruby syntax highlighting in diffs?</p>
  <p>As an example of a tool that does this - if you look at diffs on github the code syntax highlighting is there, as well as highlighting for added/removed lines.</p>