hack/verify-staging-imports.sh: check that plugins are not imported by default

hack/verify-staging-imports.sh

@@ -77,4 +77,12 @@ if grep -rq '// import "k8s.io/kubernetes/' 'staging/'; then
 	exit 1
 fi
 
+for EXAMPLE in vendor/k8s.io/client-go/examples/{in-cluster,out-of-cluster,third-party-resources}; do
+	test -d "${EXAMPLE}" # make sure example is still there
+	if go list -f '{{ join .Deps "\n" }}' "./${EXAMPLE}/..." | sort | uniq | grep -q k8s.io/client-go/plugin; then
+		echo "${EXAMPLE} imports client-go plugins by default, but shouldn't."
+		exit 1
+	fi
+done
+
 exit 0

staging/src/k8s.io/client-go/examples/out-of-cluster/main.go

@@ -25,6 +25,8 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/tools/clientcmd"
+	// Uncomment the following line to load the gcp plugin (only required to authenticate against GKE clusters).
+	// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
 )
 
 func main() {

staging/src/k8s.io/client-go/examples/third-party-resources/main.go

@@ -31,9 +31,8 @@ import (
 	"k8s.io/client-go/pkg/apis/extensions/v1beta1"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
-
-	// Only required to authenticate against GKE clusters
-	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
+	// Uncomment the following line to load the gcp plugin (only required to authenticate against GKE clusters).
+	// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
 )
 
 func main() {

vendor/BUILD

@@ -11766,7 +11766,6 @@ go_library(
         "//vendor:k8s.io/client-go/kubernetes",
         "//vendor:k8s.io/client-go/pkg/api",
         "//vendor:k8s.io/client-go/pkg/apis/extensions/v1beta1",
-        "//vendor:k8s.io/client-go/plugin/pkg/client/auth/gcp",
         "//vendor:k8s.io/client-go/rest",
         "//vendor:k8s.io/client-go/tools/clientcmd",
     ],