<nav>

{% assign ordered_collections = site.collections | sort:"order","last" %}
{% for c in ordered_collections %}
    {% if c.indexPage == nil %}
        {% assign firstDoc = c.docs | sort:"order","last" | first %}
        {% if c.title != nil %}
            <a href="{{ site.baseurl }}{{ firstDoc.url }}">{{c.title}}</a>
        {% endif %}
    {% else %}
        <a href="{{ site.baseurl }}{{ c.indexPage }}">{{c.title}}</a>
    {% endif %}
{% endfor %}
<a href="{{site.github.repository_url}}">Github</a>

</nav>