return gomod, nil
	}
	data, err = r.code.ReadFile(ctx, rev, path.Join(dir, "go.mod"), codehost.MaxGoMod)
	if err != nil {
		if os.IsNotExist(err) {
			return LegacyGoMod(r.modPath), nil
		}
		return nil, err
	}
	return data, nil
}

// LegacyGoMod generates a fake go.mod file for a module that doesn't have one.
// The go.mod file contains a module directive and nothing else: no go version,
// no requirements.
//

// and simpler.
func versionHasGoMod(_ context.Context, m module.Version) (bool, error) {
	_, data, err := rawGoModData(m)
	if err != nil {
		return false, err
	}
	isFake := bytes.Equal(data, modfetch.LegacyGoMod(m.Path))
	return !isFake, nil
}

// A versionRepo is a subset of modfetch.Repo that can report information about
// available versions, but cannot fetch specific source files.
type versionRepo interface {