Single tree record from the 'TREE' DirCache extension. A valid cache tree record contains the object id of a tree object and the total number of DirCacheEntry instances (counted recursively) from the DirCache contained within the tree. This information facilitates faster traversal of the index and quicker generation of tree objects prior to creating a new commit. An invalid cache tree record indicates a known subtree whose file entries have changed in ways that cause the tree to no longer have a known object id. Invalid cache tree records must be revalidated prior to use.