@Internal
  public List<ExtraDirectoryParameters> getPaths() {
    // Gradle warns about @Input annotations on File objects, so we have to expose a getter for a
    // String to make them go away.
    String property = System.getProperty(PropertyNames.EXTRA_DIRECTORIES_PATHS);
    if (property != null) {
      List<String> pathStrings = ConfigurationPropertyValidator.parseListProperty(property);
      return pathStrings.stream()
          .map(path -> new ExtraDirectoryParameters(objects, project, Paths.get(path), "/"))
          .collect(Collectors.toList());
    }
    if (paths.get().isEmpty()) {
      return Collections.singletonList(
          new ExtraDirectoryParameters(
              objects,
              project,
              project.getProjectDir().toPath().resolve("src").resolve("main").resolve("jib"),
              "/"));
    }
    return paths.get();
  }
Object in {@link JibExtension} that configures the extra directories.
jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/ExtraDirectoriesParameters.java