docs: private static Set<File> getMatchingDescendants(File f, List<String>[] stackLists) {
  
  		Set<File> rslt = new TreeSet<File>();
  
  		for (List<String> stack : stackLists) {
  			rslt.addAll(getMatchingDescendants(f, stack));
  		}
  
  		return rslt;
  
  	}