Add go mod tidy clean verifier to CI

.circleci/config.yml

@@ -56,6 +56,7 @@ jobs:
             - go-mod-v1-{{ checksum "go.sum" }}
       - run: make lint
       - run: ./hack/verify-generate.sh
+      - run: ./hack/verify-go-clean.sh
       - save_cache:
           key: go-mod-v1-{{ checksum "go.sum" }}
           paths:

hack/verify-go-clean.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+#####
+#  Used to ensure that running `go mod tidy` results in a non-dirty repository.
+#  Used to verify that dependency changes have been cleaned
+#####
+
+set -o nounset
+set -o pipefail
+# intentionally not setting 'set -o errexit' because we want to print custom error messages
+
+# versions of tools
+echo "$(go version)"
+
+# make sure make generate can be invoked
+go mod tidy
+RETVAL=$?
+if [[ ${RETVAL} != 0 ]]; then
+    echo "Invoking 'go mod tidy' ends with non-zero exit code."
+    exit 1
+fi
+
+git diff --exit-code --quiet
+RETVAL=$?
+
+if [[ ${RETVAL} != 0 ]]; then
+    echo "Running 'go mod tidy' produces changes to the current git status. Maybe you forgot to clean go.mod after changing dependencies?"
+    echo "The current diff:"
+    git diff
+    exit 1
+fi
+
+echo "Verifying 'go mod tidy' was successful! ヽ(•‿•)ノ"
+exit 0