Ask for confirmation before disabling OpenShift CVO

When subctl join is run against an OpenShift cluster with a deployed
cluster version operator, and service discovery is enabled, we now ask
for confirmation before continuing, because installing service
discovery will disable the CVO.

Fixes: submariner-io#167
Signed-off-by: Stephen Kitt <skitt@redhat.com>

pkg/subctl/cmd/join.go

@@ -115,6 +115,21 @@ func joinSubmarinerCluster(config *rest.Config, subctlData *datafile.SubctlData)
 	// Missing information
 	var qs = []*survey.Question{}
 
+	if subctlData.ServiceDiscovery {
+		cvoEnabled, err := isOpenShiftCVOEnabled(config)
+		exitOnError("Unable to check for the OpenShift CVO", err)
+		if cvoEnabled {
+			// Out of sequence question so we can abort early
+			disable := false
+			survey.AskOne(&survey.Confirm{
+				Message: "Enabling service discovery on OpenShift will disable OpenShift updates, do you want to continue?",
+			}, &disable)
+			if !disable {
+				return
+			}
+		}
+	}
+
 	if valid, _ := isValidClusterID(clusterID); !valid {
 		qs = append(qs, &survey.Question{
 			Name:   "clusterID",
@@ -327,6 +342,22 @@ func isValidClusterID(clusterID string) (bool, error) {
 	return true, nil
 }
 
+func isOpenShiftCVOEnabled(config *rest.Config) (bool, error) {
+	_, clientSet, err := getClients(config)
+	if err != nil {
+		return false, err
+	}
+	deployments := clientSet.AppsV1().Deployments("openshift-cluster-version")
+	scale, err := deployments.GetScale("cluster-version-operator", metav1.GetOptions{})
+	if err != nil {
+		if k8serrs.IsNotFound(err) {
+			return false, nil
+		}
+		return false, err
+	}
+	return scale.Spec.Replicas > 0, nil
+}
+
 func populateSubmarinerSpec(subctlData *datafile.SubctlData) submariner.SubmarinerSpec {
 	brokerURL := subctlData.BrokerURL
 	if idx := strings.Index(brokerURL, "://"); idx >= 0 {