def regenerate?(document)
      case document
      when Page
        regenerate_page?(document)
      when Document
        regenerate_document?(document)
      else
        source_path = document.respond_to?(:path) ? document.path : nil
        dest_path = if document.respond_to?(:destination)
                      document.destination(@site.dest)
                    end
        source_modified_or_dest_missing?(source_path, dest_path)
      end
    end
def regenerate?(document)
      case document
      when Page
        regenerate_page?(document)
      when Document
        regenerate_document?(document)
      else
        source_path = document.respond_to?(:path) ? document.path : nil
        dest_path = if document.respond_to?(:destination)
                      document.destination(@site.dest)
                    end
        source_modified_or_dest_missing?(source_path, dest_path)
      end
    end
Checks if a renderable object needs to be regenerated

 Returns a boolean.