Some of the tests on the name query operate on test modules or module cache
trees that are checked in as testdata. When the tests run, they can modify
the go.mod files and the cache tree directories. Copy the directories
to a temporary directory to avoid getting spurious git diffs showing up.
Change-Id: I991a4510201988d596833faea88425a335d3228b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/167859
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
e6df0c1bb3