module Sprockets::Rails::Helper

def asset_digest(path, options = {})

Returns String Hex digest or nil if digests are disabled.

options - Hash options
path - String path

Get digest for asset path. 
def asset_digest(path, options = {})
  return unless digest_assets
  if digest_path = asset_digest_path(path, options)
    digest_path[/-(.+)\./, 1]
  end
end