Path getDigestOutputPath() {
    Path configuredPath =
        outputPaths.digest == null
            ? Paths.get(getProject().getBuild().getDirectory()).resolve("jib-image.digest")
            : outputPaths.digest.toPath();
    return getRelativeToProjectRoot(configuredPath, PropertyNames.OUTPUT_PATHS_DIGEST);
  }
Gets the configured extra layer file permissions.

@return the configured extra layer file permissions
jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/JibPluginConfiguration.java