kartongips: switch default diff behaviour to subset, nag users

Change-Id: I998cdf7e693f6d1ce86c7ea411f47320d72a5906
diff --git a/cluster/tools/kartongips/pkg/kubecfg/diff.go b/cluster/tools/kartongips/pkg/kubecfg/diff.go
index 5d32b9e..fd21043 100644
--- a/cluster/tools/kartongips/pkg/kubecfg/diff.go
+++ b/cluster/tools/kartongips/pkg/kubecfg/diff.go
@@ -50,8 +50,6 @@
 	Mapper           meta.RESTMapper
 	DefaultNamespace string
 	OmitSecrets      bool
-
-	DiffStrategy string
 }
 
 func (c DiffCmd) Run(ctx context.Context, apiObjects []*unstructured.Unstructured, out io.Writer) error {
@@ -89,10 +87,8 @@
 		}
 
 		liveObjObject := liveObj.Object
-		if c.DiffStrategy == "subset" {
-			liveObjObject = removeMapFields(obj.Object, liveObjObject)
-			liveObjObject = removeClusterRoleAggregatedRules(liveObjObject)
-		}
+		liveObjObject = removeMapFields(obj.Object, liveObjObject)
+		liveObjObject = removeClusterRoleAggregatedRules(liveObjObject)
 
 		liveObjText, _ := json.MarshalIndent(liveObjObject, "", "  ")
 		objText, _ := json.MarshalIndent(obj.Object, "", "  ")