fix(EC-1778): use scheme-based dispatch to avoid misrouting bare hostnames

The OCI Matcher matches localhost/127.0.0.1 as known registries, which
misroutes git-over-HTTP sources hosted on localhost in acceptance tests.
Dispatch to custom gatherers only for explicit oci:// or http(s)://
scheme prefixes; bare hostnames fall through to the registry where
git matchers are checked before OCI matchers.

reference: EC-1778

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: robnester-rh

internal/downloader/downloader.go

@@ -52,18 +52,23 @@ var (
 var gatherFunc = func(ctx context.Context, source, destination string) (metadata.Metadata, error) {
 	initialize()
 
+	// Dispatch to custom gatherers only for unambiguous scheme prefixes.
+	// Bare hostnames (e.g. quay.io/..., 127.0.0.1/...) fall through to
+	// the registry, which checks git matchers before OCI matchers.
 	switch {
-	case ociGatherer.Matcher(source):
+	case strings.HasPrefix(source, "oci://") || strings.HasPrefix(source, "oci::"):
 		return ociGatherer.Gather(ctx, source, destination)
-	case httpGatherer.Matcher(source):
-		return httpGatherer.Gather(ctx, source, destination)
-	default:
-		g, err := registry.GetGatherer(source)
-		if err != nil {
-			return nil, err
+	case strings.HasPrefix(source, "https://") || strings.HasPrefix(source, "http://"):
+		if httpGatherer.Matcher(source) {
+			return httpGatherer.Gather(ctx, source, destination)
 		}
-		return g.Gather(ctx, source, destination)
 	}
+
+	g, err := registry.GetGatherer(source)
+	if err != nil {
+		return nil, err
+	}
+	return g.Gather(ctx, source, destination)
 }
 
 var _initialize = func() {

internal/downloader/downloader_test.go

@@ -159,7 +159,6 @@ func TestOCITracing(t *testing.T) {
 	t.Cleanup(trace.Stop)
 
 	log.Level = logrus.TraceLevel
-	initialize = _initialize // we want it to re-execute for the test
 	t.Cleanup(func() {
 		log.Level = logrus.InfoLevel
 		initialize = sync.OnceFunc(_initialize)
@@ -179,7 +178,12 @@ func TestOCITracing(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, remote.Push(ref, img))
 
-	_, err = gatherFunc(context.Background(), ref.String(), t.TempDir())
+	// Initialize directly then call ociGatherer.Gather to test the OCI
+	// tracing path. Bare localhost refs fall through to the registry's
+	// default gatherer (no tracing), so we invoke the gatherer directly.
+	_initialize()
+
+	_, err = ociGatherer.Gather(context.Background(), ref.String(), t.TempDir())
 	require.NoError(t, err)
 
 	trace.Stop()
@@ -215,6 +219,7 @@ func TestHTTPTracing(t *testing.T) {
 	t.Cleanup(trace.Stop)
 
 	log.Level = logrus.TraceLevel
+	initialize = _initialize
 	t.Cleanup(func() {
 		log.Level = logrus.InfoLevel
 		initialize = sync.OnceFunc(_initialize)
@@ -228,13 +233,7 @@ func TestHTTPTracing(t *testing.T) {
 	}))
 	t.Cleanup(server.Close)
 
-	// Initialize directly to set up tracing transport, then call
-	// httpGatherer.Gather to test the HTTP path specifically.
-	// (127.0.0.1 matches the OCI registry pattern, so gatherFunc
-	// would dispatch to the OCI gatherer instead of HTTP.)
-	_initialize()
-
-	_, err := httpGatherer.Gather(context.Background(), fmt.Sprintf("%s/foo", server.URL), path.Join(t.TempDir(), "dl"))
+	_, err := gatherFunc(context.Background(), fmt.Sprintf("%s/foo", server.URL), path.Join(t.TempDir(), "dl"))
 	require.NoError(t, err)
 
 	trace.Stop()