fix: ignore error of manifest tag path not found in gc

it is reasonable to ignore the error that the manifest tag path does not exist when querying
all tags of the specified repository when executing gc.

Signed-off-by: Liang Zheng <zhengliang0901@gmail.com>

registry/storage/garbagecollect.go

@@ -73,7 +73,8 @@ func MarkAndSweep(ctx context.Context, storageDriver driver.StorageDriver, regis
 					// which means that we need check (and delete) those references when deleting manifest
 					allTags, err := repository.Tags(ctx).All(ctx)
 					if err != nil {
-						if _, ok := err.(distribution.ErrManifestUnknownRevision); !ok {
+						if _, ok := err.(distribution.ErrRepositoryUnknown); ok {
+							emit("manifest tags path of repository %s does not exist", repoName)
 							return nil
 						}
 						return fmt.Errorf("failed to retrieve tags %v", err)

registry/storage/garbagecollect_test.go

@@ -416,6 +416,39 @@ func TestDeleteManifestIndexIfTagNotFound(t *testing.T) {
 	}
 }
 
+func TestGCWithUnknownRepository(t *testing.T) {
+	ctx := dcontext.Background()
+	d := inmemory.New()
+
+	registry := createRegistry(t, d)
+	repo := makeRepository(t, registry, "nonexistentrepo")
+	image := uploadRandomSchema2Image(t, repo)
+
+	err := repo.Tags(ctx).Tag(ctx, "image", distribution.Descriptor{Digest: image.manifestDigest})
+	if err != nil {
+		t.Fatalf("Failed to tag descriptor: %v", err)
+	}
+
+	// Simulate a missing _manifests/tags directory
+	manifestTagsPath, err := pathFor(manifestTagsPathSpec{"nonexistentrepo"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = d.Delete(ctx, manifestTagsPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = MarkAndSweep(dcontext.Background(), d, registry, GCOpts{
+		DryRun:         false,
+		RemoveUntagged: true,
+	})
+	if err != nil {
+		t.Fatalf("got error: %v, expected nil", err)
+	}
+}
+
 func TestGCWithMissingManifests(t *testing.T) {
 	ctx := dcontext.Background()
 	d := inmemory.New()