cmd/go: line added to go.sum with no change in requirements

[myitcv]

What version of Go are you using (go version)?

$ go version
go version devel +8e0be05ec7 Sun Jan 19 14:04:09 2020 +0000 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/myitcv/.cache/go-build"
GOENV="/home/myitcv/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/myitcv/gostuff"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/myitcv/gos"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/myitcv/gos/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/myitcv/gostuff/src/github.com/myitcv/govim/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build872676544=/tmp/go-build -gno-record-gcc-switches"

What did you do?

A recent commit that was merged for govim added a line to go.sum when there was no obvious change in requirements:

cd $(mktemp -d)
git clone https://github.com/govim/govim
cd govim
git checkout 57e94a35b8939d13fc2ff9d8e2a023db93d1cafa

Verify that we are tidy:

go mod tidy
git status

Compare go.sum to the previous commit:

git diff HEAD~1 -- go.sum

gives:

diff --git a/go.sum b/go.sum
index 309777f..b382394 100644
--- a/go.sum
+++ b/go.sum
@@ -43,6 +43,7 @@ github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81P
 golang.org/x/crypto v0.0.0-20181106171534-e4dc69e5b2fd/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550 h1:ObdrDkeb4kJdCP557AjRjq69pTHfNouLtWZG7j9rPN8=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e h1:JgcxKXxCjrA2tyDP/aNU9K0Ck5Czfk6C7e2tMw7+bSI=
 golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e/go.mod h1:mXi4GBBbnImb6dmsKGUJ2LatrhH/nqhxcFungHvyanc=

But then nothing in the commit itself changes that would, AFAIK, result in a new line in go.sum:

govim/govim@57e94a3

Am I missing something obvious here?

Credit to @leitzler for spotting this as part of a review.

What did you expect to see?

No diff in go.sum

What did you see instead?

Per above

Tentatively marking Go 1.14 in case there is something that needs fixing here.

cc @bcmills @jayconrod

[bcmills]

Duplicate of #33008

[myitcv]

Doh! I even commented on that issue. Thanks @bcmills