Add an alternate implementation for generating directory tree digests: - Do not use something like os.walk() but use os.scandir() directly. - Recursively generate the subdirectory digests only when needed and in the right order. This fixes that the order of subdirectories in the output did not match the application order of its directory digests. The new implementation also should make filtering (that will be implemented later) easier. NOTE: The tree digests of the old and the new implementation are identical.