use_relative_controller!

# File actionpack/lib/action_dispatch/routing/route_set.rb, line 575
        def use_relative_controller!
          if !named_route && different_controller? && !controller.start_with?("/")
            old_parts = current_controller.split('/')
            size = controller.count("/") + 1
            parts = old_parts[0...-size] << controller
            @options[:controller] = parts.join("/")
          end
        end