cmd/go: clean paths before using them form index functions
We use str.TrimFilePathPrefix to trim the module root prefix and get the
relative path of each package in the module when scanning the module
and in the RelPath function. Make sure to clean the path before
indexing and in RelPath to ensure that each path starts with that
prefix, because walk will clean the root path before joining each
subdirectory path to it.
Change-Id: I1dc1eddbd42030eb6d5d8e76a8675f94216447c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/411118
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org>