func helperCommand(t *testing.T, name string, args ...string) *exec.Cmd {
	t.Helper()
	return helperCommandContext(t, nil, name, args...)
}

// helperCommandContext is like helperCommand, but also accepts a Context under
// which to run the command.
func helperCommandContext(t *testing.T, ctx context.Context, name string, args ...string) (cmd *exec.Cmd) {
	helperCommandUsed.LoadOrStore(name, true)