default reference policy when updating an imagestreamtag

Author: bparees

pkg/image/registry/imagestreamtag/rest.go

@@ -269,6 +269,10 @@ func (r *REST) Update(ctx apirequest.Context, tagName string, objInfo rest.Updat
 		tagRef.Name = tag
 	}
 	tagRef.Annotations = istag.Annotations
+
+	if len(tagRef.ReferencePolicy.Type) == 0 {
+		tagRef.ReferencePolicy.Type = imageapi.SourceTagReferencePolicy
+	}
 	imageStream.Spec.Tags[tag] = tagRef
 
 	// mutate the image stream