public static boolean isFolder(final ExplorerNode node) {
        if (node == null) {
            return false;
        } else {
            DocRef docRef = node.getDocRef();
            if (docRef == null) {
                return false;
            } else {
                String type = docRef.getType();
                return type.equals(FOLDER_TYPE)
                       || type.equals(GitRepoDoc.TYPE);
            }
        }
    }
Tests whether a node is a folder.
The node is a folder if its type is FOLDER_TYPE or
GitDocRepo.TYPE.
stroom-core-shared/src/main/java/stroom/explorer/shared/ExplorerConstants.java