allow output patch string in edit command

pkg/kubectl/cmd/util/editor/editoptions.go

@@ -52,6 +52,7 @@ type EditOptions struct {
 	resource.FilenameOptions
 
 	Output             string
+	OutputPatch        bool
 	WindowsLineEndings bool
 
 	cmdutil.ValidateOptions
@@ -95,6 +96,10 @@ func (o *EditOptions) Complete(f cmdutil.Factory, out, errOut io.Writer, args []
 	}
 	o.editPrinterOptions = getPrinter(o.Output)
 
+	if o.OutputPatch && o.EditMode != NormalEditMode {
+		return fmt.Errorf("the edit mode doesn't support output the patch")
+	}
+
 	cmdNamespace, enforceNamespace, err := f.DefaultNamespace()
 	if err != nil {
 		return err
@@ -452,6 +457,10 @@ func (o *EditOptions) visitToPatch(
 			}
 		}
 
+		if o.OutputPatch {
+			fmt.Fprintf(o.Out, "Patch: %s\n", string(patch))
+		}
+
 		patched, err := resource.NewHelper(info.Client, info.Mapping).Patch(info.Namespace, info.Name, patchType, patch)
 		if err != nil {
 			fmt.Fprintln(o.ErrOut, results.addError(err, info))