Capistrano task to version files via their names so that they are cacheable as possible (vs query strings). Bases versions on the file contents so that versions are changed as infrequently as possible, and automatically. Updates all references to the static files.

deploy.rb

namespace :build do
  desc "Name static files by version"
  task :version, :roles => :app do
    find_static_files = "find #{current_release} -name '*.js' -o -name '*.css'"

    capture(find_static_files).split("\n").each do |file|
      # Get paths
      full_path = file.chomp
      relative_path = full_path.clone
      relative_path["#{current_release}/"] = ''

      # Build new file name based on hash
      parts = relative_path.split "."
      ext = parts.pop
      hash = Digest::MD5.hexdigest(capture "cat #{full_path}")
      new_relative_path = "#{parts.join('.')}.#{hash}.#{ext}"

      # Rename the file
      run "mv #{full_path} #{current_release}/#{new_relative_path}"

      # Replace refereces to the file
      search = Regexp.escape(relative_path).gsub "/", "\\/"
      replace = Regexp.escape(new_relative_path).gsub "/", "\\/"
      run "find #{current_release} -type f -exec perl -i -lpe 's/#{search}/#{replace}/g' {} \\;"
    end
  end
end