func selectPackage(dir, rel string, packageMap map[string]*Package) (*Package, error) {
	if len(packageMap) == 0 {
		return nil, nil
	}
	if len(packageMap) == 1 {
		for _, pkg := range packageMap {
			return pkg, nil
		}
	}
	defaultPackageName := strings.Replace(rel, "/", "_", -1)
	for _, pkg := range packageMap {
		if pkgName := goPackageName(pkg); pkgName != "" && pkgName == defaultPackageName {
			return pkg, nil
		}
	}
	return nil, fmt.Errorf("%s: directory contains multiple proto packages. Gazelle can only generate a proto_library for one package.", dir)
}
func selectPackage(dir, rel string, packageMap map[string]*Package) (*Package, error) {
	if len(packageMap) == 0 {
		return nil, nil
	}
	if len(packageMap) == 1 {
		for _, pkg := range packageMap {
			return pkg, nil
		}
	}
	defaultPackageName := strings.Replace(rel, "/", "_", -1)
	for _, pkg := range packageMap {
		if pkgName := goPackageName(pkg); pkgName != "" && pkgName == defaultPackageName {
			return pkg, nil
		}
	}
	return nil, fmt.Errorf("%s: directory contains multiple proto packages. Gazelle can only generate a proto_library for one package.", dir)
}
// selectPackage chooses a package to generate rules for.