gistfile1.rb

 def run_callback_from_file(callback_file)
   if whyrun_mode?
      recipe_eval { }
   else 
      if ::File.exist?(callback_file)
        Dir.chdir(release_path) do
          Chef::Log.info "#{@new_resource} running deploy hook #{callback_file}"
          recipe_eval { from_file(callback_file) }
        end
      end
    end
 end