public static String ensureRegistryHttpUrl(String registry) {
        if (registry.toLowerCase().startsWith("http")) {
            return registry;
        }
        // Default to https:// schema
        return "https://" + registry;
    }
Return the first non null registry given. Use the env var DOCKER_REGISTRY as final fallback
@param checkFirst list of registries to check
@return registry found or null if none.
src/main/java/io/fabric8/maven/docker/util/EnvUtil.java