WIP: fix annoying extraneous whitespace causing havoc with pre-commit hook.

--HG--
extra : amend_source : 302e1440f81b761b09f4ebd0fdb10c9603cf74a6
WIP step 16 - got all the unit tests passing again! Realised that relaxed
matching should only occur for removal - addition needs to use strict matching,
and also needs to introduce branches into the SharedPathPrefix for wildcard
vs determinate matches in both directions across the SharedPathPrefix against
the new partial test vector representation.