An unanchored exclude pattern such as **/node_modules or **/*.pyc
needed a / before the name, so it excluded sub/node_modules and
sub/y.pyc but backed up node_modules/ and x.pyc directly under the
snapshot path. An unanchored pattern already matches at every depth,
so the leading **/ is now dropped when the pattern is compiled and,
as in gitignore, the pattern matches the top level too.
Judgement call: an anchored /**/x is left as it was; the issue covers
patterns that start with **/.
Model: opus-5-5
sneak