gha: run unit-tests in go modules mode, to prevent traversing nested modules

`go list` expects a module to be valid, which means that dependencies must
either be vendored, or downloaded in the module cache. However, when working
in GOPATH mode, `go.mod` files are ignored, which means that `go list` will
traverse subdirectories, even if those are a separate module, and those modules
may not have their dependencies present.

In our case, we try to exclude those modules from paths to be tested, but
do so based on the _result_ of `go list`, which already produces errors before
we filter.

These errors do not impact out tests, as we don't run tests for those paths,
but do produce noise in CI, which can be confusing;

    go test -coverprofile=/tmp/coverage.txt $(go list ./... | grep -vE '/vendor/|/e2e/|/cmd/docker-trust')
    cmd/docker-trust/internal/trust/trust.go:28:2: cannot find package "github.com/theupdateframework/notary" in any of:
        /go/src/github.com/docker/cli/vendor/github.com/theupdateframework/notary (vendor tree)
        /usr/local/go/src/github.com/theupdateframework/notary (from $GOROOT)
        /go/src/github.com/theupdateframework/notary (from $GOPATH)
    cmd/docker-trust/internal/trust/trust.go:29:2: cannot find package "github.com/theupdateframework/notary/client" in any of:
        /go/src/github.com/docker/cli/vendor/github.com/theupdateframework/notary/client (vendor tree)
        /usr/local/go/src/github.com/theupdateframework/notary/client (from $GOROOT)
        /go/src/github.com/theupdateframework/notary/client (from $GOPATH)

This patch adds a symlink for `go.mod` and `go.sum`, so that listing the
packages happens in go modules mode, and doesn't traverse to other modules,
such as `cmd/docker-trust`.

- updates 06914dd, which attempted to
  exclude the docker-trust plugin
- similar to cee9ea6, which made this
  change for the linter.

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

.github/workflows/test.yml

@@ -71,7 +71,10 @@ jobs:
       -
         name: Test
         run: |
-          go test -coverprofile=/tmp/coverage.txt $(go list ./... | grep -vE '/vendor/|/e2e/|/cmd/docker-trust')
+          # run in go modules mode to prevent traversing to nested modules
+          ln -s vendor.mod go.mod
+          ln -s vendor.sum go.sum
+          go test -coverprofile=/tmp/coverage.txt $(go list ./... | grep -vE '^github.com/docker/cli/e2e/')
           go tool cover -func=/tmp/coverage.txt
         working-directory: ${{ env.GOPATH }}/src/github.com/docker/cli
         shell: bash