routes.rb

Dummy::Application.routes.draw do

  sections '/cms' do
    section :bar, to: 'test#welcome2'

    #section :bar do
    #  get ":id", to: 'test#welcome'
    #end

    get "/welcome" => 'test#welcome', section: :foo
    root to: 'test#welcome'
  end

end

routing.rb

require "singleton"

module Hg
  class Routing

    def self.setup(router, root = '/', &block)
      raise Hg::MissingBlock unless block_given?
      new(router, root, &block)
    end

    def initialize(router, root, &block)
      @router = router
      @root = root
      @mapper = Mapper.new
      context = self
      scope(root) do
        constraints(Hg::SectionConstraint.new(false)) do
          context.instance_eval(&block)
        end
        constraints(Hg::SectionConstraint.new(true, @mapper)) do
          get '*path', to: 'hg/section#show', format: false
        end
      end
    end

    def section(name, options)
      @mapper[name] = options
    end

    def method_missing(method, *args, &block)
      if @router.respond_to?(method, true)
        @router.send(method, *args, &block)
      else
        super
      end
    end

    class Mapper

      def initialize
        @sections = {}
      end

      def []=(name, options)
        @sections[name] = options
      end

      def [](name)
        @sections[name]
      end

    end

  end
end

# inject our method into ActionDispatch::Routing::Mapper

module ActionDispatch
  module Routing
    class Mapper

      def sections(root, &block)
        ::Hg::Routing.setup(self, root, &block)
      end

    end
  end
end