[release-branch.go1.15] cmd/go: use path.Dir instead of filepath.Dir for package paths in 'go mod vendor'
copyMetadata walk-up to parent directory until the pkg become modPath.
But pkg should be slash-separated paths. It have to use path.Dir instead of
filepath.Dir.
Updates #46867
Fixes #47014
Change-Id: I44cf1429fe52379a7415b94cc30ae3275cc430e8
Reviewed-on: https://go-review.googlesource.com/c/go/+/330149
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Trust: Bryan C. Mills <bcmills@google.com>
Trust: Alexander Rakoczy <alex@golang.org>
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
(cherry picked from commit
835d86a17ebf32a3cb081f66119c74363dbd8825)
Reviewed-on: https://go-review.googlesource.com/c/go/+/332330
Reviewed-by: Jay Conrod <jayconrod@google.com>
Run-TryBot: Carlos Amedee <carlos@golang.org>