minify js and css files

assets.yml

# These files will be minified ...
javascripts:
  - build/js/ga.js
  - build/js/jquery-1.7.1.js
  - build/js/portfolio.js

styles:
  - build/style/screen_v3.css

# And combined into single files
outputjs: build/js/client.js
outputcss: build/style/style.css

rakefile.rb

require 'yaml'
require 'yui/compressor'

desc 'minify all the things'
task :min do
  assets = YAML.load_file 'assets.yml'

  outjs  = File.new assets['outputjs'], 'w'
  outcss = File.new assets['outputcss'], 'w'

  js  = assets[ 'javascripts' ].collect{ |f| IO.read("#{f}") }
  css = assets[ 'styles' ].collect{ |f| IO.read("#{f}") }

  js_compressor  = YUI::JavaScriptCompressor.new :munge => true
  css_compressor = YUI::CssCompressor.new

  outjs.write js_compressor.compress( js.join ' ' )
  outcss.write css_compressor.compress( css.join ' ' )

end