_includes/sidebar.html

<div class="sidebar">
  <div class="container sidebar-sticky">
    <div class="sidebar-about">
      <h1>
        <a href="{{ site.baseurl }}">
          <img alt="OpenZipkin logo" src="{{ site.baseurl }}public/img/zipkin-logo-200x119.jpg"
          style="border: 10px solid white">
        </a>
      </h1>
      <p class="lead">{{ site.tagline }}</p>
    </div>

    <nav class="sidebar-nav">

      {% assign pages_list = site.pages %}
      {% for node in pages_list %}
        {% if node.title != null %}
          {% if node.layout == "page" %}
            <a class="sidebar-nav-item{% if page.url == node.url %} active{% endif %}" href="{{ node.url }}">{{ node.title }}</a>
          {% endif %}
        {% endif %}
      {% endfor %}
    </nav>

    <p>&copy; {{ site.time | date: '%Y' }}. All rights reserved.</p>
  </div>
</div>