pkg/manifests.list.preferOCI(): pay attention annotations in indexes

Account for the presence of annotations in the OCI version of an index
or list when deciding if the structure should be saved in OCI format.
This requires removing an annotation from the test data so that the
presence of "features" information for one of its instances will be the
deciding factor.

If we don't take those into account, setting annotations in the index
doesn't force the index to be saved in OCI format, even with none of the
indicators present that would force use of the Docker format,
effectively throwing away those annotations.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

pkg/manifests/manifests.go

@@ -469,6 +469,9 @@ func (l *list) preferOCI() bool {
 	if l.oci.Subject != nil {
 		return true
 	}
+	if len(l.oci.Annotations) > 0 {
+		return true
+	}
 	for _, m := range l.oci.Manifests {
 		if m.ArtifactType != "" {
 			return true

pkg/manifests/testdata/fedora.index.json

@@ -38,8 +38,5 @@
             "size": 529
         }
     ],
-    "schemaVersion": 2,
-    "annotations": {
-      "foo": "bar"
-    }
+    "schemaVersion": 2
 }