windows: avoid deleting non-empty reparse points
If a hg repository including working directory is a reparse point (directory
symlinked or a junction point), then using os.removedirs will remove the
reparse point erroneously. This is fixed by only removing directories if they
are empty.
% change the id of the tree root
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Initial add
0 Changed root
% manifest of tip
644 file