Match retina images

In my nanoc project, I need to use retina images (same image ending with @2x by convention, for use with Retina.js/a compass mixin). This is my rule:

    route %r{/(images)/*/} do
      # cache-bust images
      if item.identifier.chop.end_with?('@2x')
        item.identifier.chop[0..-4] + fingerprint(item[:filename]) + '@2x.' + item[:extension]
      else
        item.identifier.chop + fingerprint(item[:filename]) + '.' + item[:extension]
      end
    end

I needed to modify the CSS strategy to allow for matching Retina images. I'll try to write a cucumber test if I have time, but I'm on Windows at the moment and rspec doesn't like to play well on here. :(