match: use match.prefix() in subdirmatcher It seems like the subdirmatcher should be checking if the matcher it's based on is matching prefixes. It was effectively doing that already because "prefix() == not always() and not anypats() and not isexact()", subdirmatcher was checking the first two parts of that condition and I don't think it will ever be given an "exact" matcher with it's directory name (because exact matchers are for matching files, not directories). Still, let's switch to using prefix() for clarity (and because I'm trying to remove code that reaches for matchers internals).