The prototype for the new path-walking logic in 3.3 Unicode
path normalization.  This Oct-2022 recoding handles more
folder syntax than its predecessor.  

See the docstr at the top of py-split-join.py for details. 
This logic has now been adopted in Mergeall's:

    fixunicodedups.matchUnicodePathnames()

which is tested/demoed on actual content in the ../test* folder.