cmd/go: avoid matching wildcards rooted outside of available modules
To avoid confusion, also distinguish between packages and dirs in
search.Match results.
No test because this is technically only a performance optimization:
it would be very difficult to write such a test so that it would not
be flaky. (However, tested the change manually.)
Fixes #37521
Change-Id: I17b443699ce6a8f3a63805a7ef0be806f695a4b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/221544
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>