Using sprockets outside of rails

Rakefile

require 'rubygems'
require 'sprockets'

task :default => [:release]

desc "Release the application"
task :release do
  puts "Compiling JavaScript assets...hang tight!"
  project_root = File.expand_path(File.dirname(__FILE__))
  assets = Sprockets::Environment.new(project_root)
  assets.append_path(File.join(project_root, 'javascripts'))
  manifest = assets['manifest.js']

  outpath = File.join(project_root, 'release')
  outfile = Pathname.new(outpath).join('application.min.js')

  FileUtils.mkdir_p outfile.dirname

  manifest.write_to(outfile)
  puts "Successfully compiled JavaScript assets!"
end