gistfile1.rb

original_js = File.binread("app/assets/javascripts/application.js")
if original_js.include?("require 'my_engine'")
   say_status("skipped", "insert into app/assets/javascripts/application.js", :yellow)
else
   insert_into_file "app/assets/javascripts/application.js", :after => %r{//= require ['"]?jquery['"]?} do
      "\n//= require 'my_engine'\n\n"
   end
end