cmd/go/internal/modload: fuse upgrading with downgrading in EditBuildList
Previosly, EditBuildList performed an mvs.Upgrade followed by an
mvs.Downgrade, with the Downgrade building on the result of the
Upgrade. Unfortunately, that approach potentially folds in irrelevant
dependencies from the first Upgrade, which are then preserved
unnecessarily by the Downgrade (see mod_get_downup_artifact.txt).
Now, we use the initial Upgrade only to compute the maximum allowed
versions of transitive dependencies, and apply the module upgrades and
downgrades together in a single operation.
For #36460
Change-Id: I7590c137111fed4a3b06531c88d90efd49e6943a
Reviewed-on: https://go-review.googlesource.com/c/go/+/290770
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org>