<header>

<nav class="navbar navbar-dark bg-dark navbar-expand-md">
    <a class="navbar-brand" href="{{ "/" | relative_url }}">{{ site.title | escape }}</a>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbar" aria-controls="navbar" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
    <div id="navbar" class="collapse navbar-collapse">
        <ul class="navbar-nav mr-auto">
            {% assign default_paths = site.pages | map: "path" %}
            {% assign page_paths = site.header_pages | default: default_paths %}
            {% if page_paths %}
                {% for path in page_paths %}
                    {% assign my_page = site.pages | where: "path", path | first %}
                    {% if my_page.title and my_page.autogen == nil %}
                        <li class="nav-item">
                            <a class="nav-link" href="{{ my_page.url | relative_url }}">{{ my_page.title | escape }}</a>
                        </li>
                    {% endif %}
                {% endfor %}
            {% endif %}
        </ul>
    </div>
</nav>

</header>