AssetFile.rb

input "app/assets"
output "public"

# convert coffee files into JS files
matches "*.coffee" do
  filter(CoffeeScriptFilter) do |file|
    "#{file}.js"
  end
end

# concatenate all js files into application.js, will include
# the coffeescript files in the previous step
matches "*.js" do
  filter Rake::Pipeline::ConcatFilter, "application.js"
end