fix(registry): derive the add-source id from the full IPv6 host

internal/server/add_registry_source.go

@@ -226,7 +226,7 @@ func buildRegistrySourceEntry(rawURL, protocol, id, name string) (config.Registr
 			ErrUnsupportedRegistryProtocol, protocol, defaultRegistryProtocol)
 	}
 	if id == "" {
-		id = deriveRegistryID(u.Host)
+		id = deriveRegistryID(u.Hostname())
 	}
 	if name == "" {
 		name = id
@@ -272,13 +272,11 @@ func validateNewRegistrySource(cfg *config.Config, entry config.RegistryEntry) e
 	return nil
 }
 
-// deriveRegistryID slugifies a host into a stable registry id, dropping a
-// leading "www." and a trailing port, and replacing non-alphanumerics with "-".
+// deriveRegistryID slugifies a hostname (no port, no IPv6 brackets) into a
+// stable registry id, dropping a leading "www." and replacing non-alphanumerics
+// with "-".
 func deriveRegistryID(host string) string {
 	host = strings.ToLower(host)
-	if h, _, ok := strings.Cut(host, ":"); ok {
-		host = h
-	}
 	host = strings.TrimPrefix(host, "www.")
 	var b strings.Builder
 	for _, r := range host {

internal/server/add_registry_source_ipv6_test.go

@@ -0,0 +1,25 @@
+package server
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// An IPv6 literal host contains colons. Cutting at the first ':' to drop a port
+// reduced every such host to its first group, so distinct registries collided
+// on the same derived id and the second one was refused as a duplicate.
+func TestBuildRegistrySourceEntry_IPv6HostID(t *testing.T) {
+	cases := map[string]string{
+		"https://[2606:4700:4700::1111]/":     "2606-4700-4700--1111",
+		"https://[2606:4700::64]:8443/":       "2606-4700--64",
+		"https://www.Registry.Example:8443/":  "registry-example",
+		"https://registry.acme.example/v0.1/": "registry-acme-example",
+	}
+	for raw, want := range cases {
+		entry, err := buildRegistrySourceEntry(raw, "", "", "")
+		require.NoError(t, err, raw)
+		assert.Equal(t, want, entry.ID, raw)
+	}
+}