@InputFiles
  public FileCollection getInputFiles() {
    List<Path> extraDirectories =
        Preconditions.checkNotNull(jibExtension).getExtraDirectories().getPaths().stream()
            .map(ExtraDirectoryParameters::getFrom)
            .collect(Collectors.toList());
    return GradleProjectProperties.getInputFiles(
        getProject(), extraDirectories, jibExtension.getConfigurationName().get());
  }
Returns a collection of all the files that jib includes in the image. Only used to calculate
UP-TO-DATE.

@return a list of paths of input files
jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/BuildTarTask.java