add feature gate

pkg/controller/job/job_controller.go

@@ -1482,7 +1482,10 @@ func (jm *Controller) manageJob(ctx context.Context, job *batch.Job, activePods
 					if completionIndex != unknownCompletionIndex {
 						template = podTemplate.DeepCopy()
 						addCompletionIndexAnnotation(template, completionIndex)
-						addCompletionIndexLabel(template, completionIndex)
+
+						if feature.DefaultFeatureGate.Enabled(features.PodIndexLabel) {
+							addCompletionIndexLabel(template, completionIndex)
+						}
 						template.Spec.Hostname = fmt.Sprintf("%s-%d", job.Name, completionIndex)
 						generateName = podGenerateNameWithIndex(job.Name, completionIndex)
 					}

pkg/controller/job/job_controller_test.go

@@ -962,7 +962,9 @@ func checkIndexedJobPods(t *testing.T, control *controller.FakePodControl, wantI
 	gotIndexes := sets.New[int]()
 	for _, p := range control.Templates {
 		checkJobCompletionEnvVariable(t, &p.Spec)
-		checkJobCompletionLabel(t, &p)
+		if feature.DefaultFeatureGate.Enabled(features.PodIndexLabel) {
+			checkJobCompletionLabel(t, &p)
+		}
 		ix := getCompletionIndex(p.Annotations)
 		if ix == -1 {
 			t.Errorf("Created pod %s didn't have completion index", p.Name)
@@ -4395,6 +4397,7 @@ func TestFinalizersRemovedExpectations(t *testing.T) {
 		t.Errorf("Timeout waiting for expectations (-want, +got):\n%s", diff)
 	}
 }
+
 func checkJobCompletionLabel(t *testing.T, p *v1.PodTemplateSpec) {
 	t.Helper()
 	labels := p.GetLabels()