cli/file_store: Preserve IPv6 URL normalization after Go change

Add a fallback for unbracketed IPv6 literals to preserve behavior.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

Author: vvoland

cli/config/credentials/file_store.go

@@ -117,7 +117,48 @@ func ConvertToHostname(maybeURL string) string {
 			}
 			return net.JoinHostPort(u.Hostname(), u.Port())
 		}
+
+		if hostName := hostFromURLFallback(stripped); hostName != "" {
+			return hostName
+		}
 	}
 	hostName, _, _ := strings.Cut(stripped, "/")
 	return hostName
 }
+
+// hostFromURLFallback extracts a host from scheme URLs that net/url rejects.
+// Go rejects unbracketed IPv6 literals in URL hosts since
+// https://github.com/golang/go/commit/0c28789bd7dfc55099cac86a3212dda0d6c091f6
+func hostFromURLFallback(maybeURL string) string {
+	_, rest, ok := strings.Cut(maybeURL, "://")
+	if !ok {
+		return ""
+	}
+
+	hostName, _, _ := strings.Cut(rest, "/")
+	if hostName == "" {
+		return ""
+	}
+
+	if strings.Count(hostName, ":") > 1 && !strings.HasPrefix(hostName, "[") {
+		portStart := strings.LastIndex(hostName, ":")
+		addr, port := hostName[:portStart], hostName[portStart+1:]
+		if addr != "" && isPort(port) {
+			return net.JoinHostPort(addr, port)
+		}
+	}
+
+	return hostName
+}
+
+func isPort(port string) bool {
+	if port == "" {
+		return false
+	}
+	for _, r := range port {
+		if r < '0' || r > '9' {
+			return false
+		}
+	}
+	return true
+}