code: public static Iterable<DocFile> list(Configuration configuration, Location location, DocPath path) {
          return DocFileFactory.getFactory(configuration).list(location, path);
      }
docs: List the directories and files found in subdirectories along the
  elements of the given location.
  @param configuration the doclet configuration
  @param location currently, only {@link StandardLocation#SOURCE_PATH} is supported.
  @param path the subdirectory of the directories of the location for which to
  list files