tg.t.Fatalf("internal testsuite error: path(%q) with no tempdir", name)
	}
	if name == "." {
		return tg.tempdir
	}
	return filepath.Join(tg.tempdir, name)
}

// mustExist fails if path does not exist.
func (tg *testgoData) mustExist(path string) {
	tg.t.Helper()
	if _, err := os.Stat(path); err != nil {
		if os.IsNotExist(err) {
			tg.t.Fatalf("%s does not exist but should", path)
		}