private final Node rootNode;

        PrefixFileSet(File rootDir) {
            this(toAbsolutePath(rootDir));
        }

        PrefixFileSet(String rootPath) {
            String path = removeTrailingSeparator(rootPath);
            this.rootNode = new Node(path);
        }

        PrefixFileSet(Node rootNode) {
            this.rootNode = rootNode;
        }

        @VisibleForTesting