home-assistant.io/plugins/cache_buster.rb

module Jekyll
  module CacheBuster
    require 'digest/md5'
    def cache_buster(file_name)
      [file_name, '?', Digest::MD5.hexdigest(File.read(File.join('./source', file_name)))].join
    end
  end
end

Liquid::Template.register_filter(Jekyll::CacheBuster)