Using Jammit and asset_hash with Rails 2.3.11 (Also, using my fork of asset_hash to avoid a Rails 3.x `require` conflict: https://github.com/agibralter/asset_hash)

asset_fingerprints.rb

# lib/asset_fingerprints.rb -- A hack to get asset_hash to play nice with Rails 2.3.11 (since there is no ActionController::Base.asset_path configuration option).


# Same as deployment nginx configuration.
# No font/woff because it is already compressed:
# http://www.pixelastic.com/blog/87:gzipping-your-font-files
AssetHash::Base.gzip_types = %w(
  application/javascript
  application/json
  application/xml
  application/rss+xml
  application/vnd.ms-fontobject
  image/svg+xml
  font/truetype
  font/opentype
  text/css
  text/javascript
  text/plain
  text/x-component
  text/xml
)

AssetHash::Base.asset_paths = %w(
  favicon.ico
  images
  javascripts
  stylesheets
  assets
  fonts
)

module AssetFingerprints

  @@cache = {}
  @@cache_guard = Mutex.new

  def self.included(base)
    base.class_eval do
      alias_method_chain :rewrite_asset_path, :fingerprints
    end
  end

  def rewrite_asset_path_with_fingerprints(source)
    if !@@cache[source]
      @@cache_guard.synchronize do
        @@cache[source] = AssetHash.fingerprint(source)
      end
    end
    @@cache[source]
  end
end

ActionView::Helpers::AssetTagHelper.class_eval do
  include AssetFingerprints
end

assets.rake

# lib/tasks/assets.rake

namespace :asset do

  desc 'Process css and replace urls with deployment-ready urls.'
  task :process_css => :environment do

    Dir.glob(File.join(Rails.root, 'public', 'assets', '*.css')) do |path|
      File.open(path, 'r+') do |f|
        contents = f.read
        contents.gsub!(/url\((?![^\)]*data:)(['"])?(.*?)(['"])?\)/) do |match|
          q1   = $1
          path = $2
          q2   = $3

          path.gsub!(/\?\d+/, '')
          # Some SVG fonts require the "#..." hash at the end of the url... preserve it.
          path.gsub!(/(#\w+)/, '')
          hash = $1

          path       = AssetHash.fingerprint(path)
          asset_host = "//#{ASSET_HOST}"

          "url(#{q1}#{asset_host}#{path}#{hash}#{q2})"
        end
        f.rewind
        f.truncate(contents.size)
        f << contents
      end
    end
  end
end

before_restart.rb

# config/deploy/before_restart.rb

# CHEF deploy hook

APP_ROOT = File.expand_path(File.join(File.dirname(__FILE__), "..", ".."))

def run_or_else(command)
  command = "bin/#{command}"
  system(command) or raise("before_restart: #{command} failed")
end

Dir.chdir(APP_ROOT) do
  run_or_else("compass compile --force")
  run_or_else("jammit")
  run_or_else("rake asset:process_css")
  run_or_else("rake asset:hash:generate")
  run_or_else("rake god:running_start")
end

environment.rb

# config/environment.rb

RAILS_GEM_VERSION = '2.3.11' unless defined? RAILS_GEM_VERSION

require File.join(File.dirname(__FILE__), 'boot')

Rails::Initializer.run do |config|

  # ...

  config.after_initialize do

    # ...

    ActionController::Base.asset_host = Proc.new do |source, request|
      "http#{'s' if request.ssl?}://#{ASSET_HOST}"
    end

    if Rails.env.staging? || Rails.env.production?
      require 'asset_fingerprints'
    end

    # ...

  end
end