# File lib/churn/history.rb, line 14
    def self.load_revision_data(revision, data_directory)
      #load revision data from scratch folder if it exists
      filename = "#{data_directory}/#{revision}.json"
      if File.exists?(filename)
        begin
          json_data = File.read(filename)
          data      = JSON.parse(json_data)
          changed_files   = data['churn']['changed_files']
          changed_classes = data['churn']['changed_classes']
          changed_methods = data['churn']['changed_methods']
        rescue JSON::ParserError
          #leave all of the objects nil
        end
      end
      [changed_files, changed_classes, changed_methods]
    end