no dummy resolver applied to reference resolver

Signed-off-by: Shiwei Zhang <shizh@microsoft.com>

cmd/oras/push.go

@@ -114,7 +114,11 @@ func runPush(opts pushOptions) error {
 	// bake artifact
 	var pushOpts []oras.PushOpt
 	if opts.artifactType != "" {
-		manifests, err := loadReferences(ctx, resolver, opts.artifactRefs)
+		refResolver := resolver
+		if iresolver.IsDummy(resolver) {
+			refResolver = newResolver(opts.username, opts.password, opts.insecure, opts.plainHTTP, opts.configs...)
+		}
+		manifests, err := loadReferences(ctx, refResolver, opts.artifactRefs)
 		if err != nil {
 			return err
 		}

internal/resolver/dummy.go

@@ -25,6 +25,11 @@ func Dummy() remotes.Resolver {
 	return dummyResolverInstance
 }
 
+// IsDummy checks if the resolver is dummy
+func IsDummy(resolver remotes.Resolver) bool {
+	return resolver == dummyResolverInstance
+}
+
 func (r *dummyResolver) Resolve(ctx context.Context, ref string) (name string, desc ocispec.Descriptor, err error) {
 	return "", ocispec.Descriptor{}, errors.Wrap(errdefs.ErrNotFound, "dummy resolver")
 }