gistfile1.rb

require 'rack'

module Middleware
  class Jammit
    ROOT = '/app/javascripts'

    def initialize(app, options = {})
      @app = app
      @file_server = ::Rack::File.new(Protosite::Engine.root)
    end

    def call(env)
      return @file_server.call(env) if env['PATH_INFO'].match(%r(#{ROOT}))

      @app.call(env)
    end

  end
end

app.middleware.insert_after ::ActionDispatch::Static, Middleware::Jammit