Middleman sprockets fingerprint

I'm using middleman with sprockets for packaging my js and css files into one file. This works fine. But I was wondering if it is possible to enable the fingerprint feature from sprockets in middleman.

e.g. my file all.js, in which everything gets compiled, gets renamed to all-4e17d33ff76d744900c2691a71ed83e4.js.

It would also be great, if this would be possible with images.

Solution

I haven't found a out of the box solution for this, but I made my own solution. In the config.rb I'm running the after_build hook. Not the best way, but it works:

after_build do
  require 'fileutils'
  delete_except "build/javascripts/", "all.js"
  delete_except "build/stylesheets/", "all.css"

  require 'digest/sha1'
  sha1 = Digest::SHA1.hexdigest Time.now.getutc.to_i.to_s
  allJS = "all-" + sha1 + ".js"
  allCSS = "all-" + sha1 + ".css"
  File.rename("build/javascripts/all.js", "build/javascripts/" + allJS)
  File.rename("build/stylesheets/all.css", "build/stylesheets/" + allCSS)

  index_file = "build/index.html"
  html = File.read(index_file)
  html = html.gsub(/all\.js/, allJS)
  html = html.gsub(/all\.css/, allCSS)

  File.open(index_file, "w") { |file| file.puts html }
end

I'm doing the following:

delete unnecessary generated .js and .css files
generating a sha1 hash based on time (that's enough for me)
appending the hash to the files
updating the index.html with the new file names