feat: update the implementation of deleting manifest for distribution…

…-spec v1.1.0-rc3 (#558)

Support deleting image indexes with a subject

Resolves: #535
Signed-off-by: Lixia (Sylvia) Lei <lixlei@microsoft.com>

registry/remote/repository.go

@@ -1079,7 +1079,8 @@ func (s *manifestStore) Delete(ctx context.Context, target ocispec.Descriptor) e
 // deleteWithIndexing removes the manifest content identified by the descriptor,
 // and indexes referrers for the manifest when needed.
 func (s *manifestStore) deleteWithIndexing(ctx context.Context, target ocispec.Descriptor) error {
-	if target.MediaType == spec.MediaTypeArtifactManifest || target.MediaType == ocispec.MediaTypeImageManifest {
+	switch target.MediaType {
+	case spec.MediaTypeArtifactManifest, ocispec.MediaTypeImageManifest, ocispec.MediaTypeImageIndex:
 		if state := s.repo.loadReferrersState(); state == referrersStateSupported {
 			// referrers API is available, no client-side indexing needed
 			return s.repo.delete(ctx, target, true)
@@ -1100,9 +1101,12 @@ func (s *manifestStore) deleteWithIndexing(ctx context.Context, target ocispec.D
 	return s.repo.delete(ctx, target, true)
 }
 
-// indexReferrersForDelete indexes referrers for image or artifact manifest with
-// the subject field on manifest delete.
-// Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc1/spec.md#deleting-manifests
+// indexReferrersForDelete indexes referrers for manifests with a subject field
+// on manifest delete.
+//
+// References:
+//   - https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#deleting-manifests
+//   - https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc1/spec.md#deleting-manifests
 func (s *manifestStore) indexReferrersForDelete(ctx context.Context, desc ocispec.Descriptor, manifestJSON []byte) error {
 	var manifest struct {
 		Subject *ocispec.Descriptor `json:"subject"`