gem install bagger

require 'bagger'
require 'fileutils'

# define source and target directories
target_dir = "/tmp/bundled_assets"
source_dir = "/applications/my_app/public"

# customize paths for file and cache manifest
manifest_path = File.join(target_dir, 'file_manifest.json') # defaults to manifest.json

cache_manifest_path = 'cache/cache.manifest' # defaults to cache.manifest

# list the stylesheets and javascripts to be combined
# and minified. The order is important, because otherwhise
# the behavior of the stylesheets and javascripts might change
stylesheets = ["css/style.css", "css/reset.css"]
javascripts = ["js/app.js", "js/utils.js"]

# define cache manifest bundles for different devices
# for convenience, the manifest defined with `cache_manifest_path`
# will always contain all resources
ipad_resources = ["images/troll-big.png"]
iphone_retina_resources = ["images/troll-retina.png"]
desktop_browser_resources = ["images/troll.png"]

# make sure the target directory exists
FileUtils.mkdir_p target_dir

# define the options hash
options = {
	:source_dir => source_dir,
	:target_dir => target_dir,
	:manifest_path => manifest_path,
:gzip => false,
:verbose => false,
	:cache_manifest_path => cache_manifest_path,
		:path_prefix => '',
		:css_path_prefix => '',
		:exclude_pattern => /.*\.less/,
		:exclude_files => [ 'css/main.sass', 'css/style.sass' ]
	:combine => {
	 :stylesheets => [
	    {
	      :target_path => 'css/all.css',
	      :files => stylesheets
	    }
	  ],
	 :javascripts => [
	    {
	      :target_path => 'js/combined.js',
	      :files => javascripts
	    }
	  ]
	},
	:cache_manifests => [
	  {
	    :target_path => 'cache/ipad-cache.manifest',
	    :files => ipad_resources
	  },
	  {
	    :target_path => 'cache/retina-cache.manifest',
	    :files => iphone_retina_resources
	  },
	  {
	    :target_path => 'cache/desktop.manifest',
	    :files => desktop_browser_resources
	  }
	]
}

# run it
Bagger::bagit!(options)

manifest_path = File.join(target_dir, 'manifest.json')
cache_manifest_path = File.join(target_dir, 'cache.json')

{
  "/css/all.css" : "/css/all.19db9a16e2b73017c575570de577d103.css",
  "/js/combined.js" : "/js/combined.19db9a16e2b73017c575570de577d103.js",
  "/images/logo.png" : "/images/logo.19db9a16e2b73017c575570de577d103.png" 
}

CACHE MANIFEST

# Explicitely cached entries
/css/all.19db9a16e2b73017c575570de577d103.css
/js/combined.19db9a16e2b73017c575570de577d103.js
/images/logo.19db9a16e2b73017c575570de577d103.png

NETWORK:
*