mount

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 239
        def mount(app, options = nil)
          if options
            path = options.delete(:at)
          else
            options = app
            app, path = options.find { |k, v| k.respond_to?(:call) }
            options.delete(app) if app
          end

          raise "A rack application must be specified" unless path

          match(path, options.merge(:to => app, :anchor => false, :format => false))
          self
        end