public function showHelpInfo(string $command = ''): void
    {
        /** @var \Inhere\Console\IO\Input $in */
        $in = $this->input;

        // display help for a special command
        if ($command) {
            $in->setCommand($command);
            $in->setSOpt('h', true);
            $in->clearArgs();
            $this->dispatch($command);
            return;
        }

        $sep    = $this->delimiter;
        $script = $in->getScript();

        /** @var \Inhere\Console\IO\Output $out */
        $out = $this->output;
        $out->helpPanel([
            'usage'   => "$script <info>{command}</info> [--opt -v -h ...] [arg0 arg1 arg2=value2 ...]",
            'example' => [
                "$script test (run a independent command)",
                "$script home{$sep}index (run a command of the group)",
                "$script help {command} (see a command help information)",
                "$script home{$sep}index -h (see a command help of the group)",
                "$script --auto-completion --shell-env [zsh|bash] [--gen-file stdout]",
            ]
        ]);
    }