image: add a warning when the platform is not applicable

Signed-off-by: zhouhao <zhouhao@cn.fujitsu.com>

Author: zhouhao

image/image.go

@@ -179,6 +179,10 @@ func unpack(w walker, dest, refName, platform string) error {
 	}
 
 	if ref.MediaType == validRefMediaTypes[0] {
+		if platform != "" {
+			fmt.Println("WARNING: reftype manifest does not support platform option, which are only applicable if reftype is index.")
+		}
+
 		m, err := findManifest(w, ref)
 		if err != nil {
 			return err
@@ -255,6 +259,10 @@ func createRuntimeBundle(w walker, dest, refName, rootfs, platform string) error
 	}
 
 	if ref.MediaType == validRefMediaTypes[0] {
+		if platform != "" {
+			fmt.Println("WARNING: reftype manifest does not support platform option, which are only applicable if reftype is index.")
+		}
+
 		m, err := findManifest(w, ref)
 		if err != nil {
 			return err