class IncrementalRelativeFileSets {

    public static int getBaseDirectoryCount(@NonNull ImmutableMap<RelativeFile, FileStatus> set) {
        return set.keySet()
                .stream()
                .map(RelativeFile::getBase)
                .filter(Files.isDirectory())
                .collect(Collectors.toSet())
                .size();
    }

    private  IncrementalRelativeFileSets();

}