refactor builder in kubectl factory

pkg/kubectl/cmd/diff.go

@@ -408,18 +408,12 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions, from, t
 
 	printer := Printer{}
 
-	mapper, typer, err := f.UnstructuredObject()
-	if err != nil {
-		return err
-	}
-
 	cmdNamespace, enforceNamespace, err := f.DefaultNamespace()
 	if err != nil {
 		return err
 	}
 
-	r := f.NewBuilder().
-		Unstructured(f.UnstructuredClientForMapping, mapper, typer).
+	r := f.NewUnstructuredBuilder().
 		NamespaceParam(cmdNamespace).DefaultNamespace().
 		FilenameParam(enforceNamespace, &options.FilenameOptions).
 		Flatten().