func PathToTree(path string, numTrees int64) uint64 {
	path = clean(path)
	return pathToTree(b(path), numTrees)
}
func PathToTree(path string, numTrees int64) uint64 {
	path = clean(path)
	return pathToTree(b(path), numTrees)
}
// PathToTree computes the hashtree shard for a path.