gen_url

# File lib/rdoc/generators/html_generator.rb, line 1138
    def HTMLGenerator.gen_url(path, target)
      from          = File.dirname(path)
      to, to_file   = File.split(target)
      
      from = from.split("/")
      to   = to.split("/")
      
      while from.size > 0 and to.size > 0 and from[0] == to[0]
        from.shift
        to.shift
      end
      
      from.fill("..")
      from.concat(to)
      from << to_file
      File.join(*from)
    end