Scoped engines routing

Right now, there is no control over engine routes that are injected into base app. It is impossible to mount engine at "/foo/" instead of "/"

However it could be easily done with 9 lines of code.

# Some hacking
class Rails::Engine
  def self.define_routes(&block)
    @@__routes_block = block
  end
  
  def self.draw_routes(where)
    where.instance_exec &@@__routes_block
  end
end

# then

# my_app/config/routes.rb
MyApp::Application.routes.draw do |map|
  scope "bar" do
    MyEngine::Engine.draw_routes(self)
  end
end

# my_engine.rb

require "rails"

module MyEngine
  class Engine < Rails::Engine
    define_routes do
      match "/my_engine", :to => "my_engine#foo"
    end
  end
end


# $ rake routes
# bar_my_engine  /bar/my_engine {:controller=>"my_engine", :action=>"foo"}