code: func findBuildFile(pkgPath string) (bool, string) {
  	options := []string{"BUILD.bazel", "BUILD"}
  	for _, b := range options {
  		path := filepath.Join(pkgPath, b)
  		info, err := os.Stat(path)
  		if err == nil && !info.IsDir() {
  			return true, path
  		}
  	}
  	return false, filepath.Join(pkgPath, "BUILD")
  }
docs: // findBuildFile determines the name of a preexisting BUILD file, returning
  // a default if no such file exists.