<header class="navbar navbar-expand-md navbar-light fixed-top bg-light" role="navigation">
  <!-- Main title -->
  <a class="navbar-brand" href="{{ nav.homepage.url }}">{{ config.site_name }}</a>

  <!-- Collapsed navigation -->
  {% if nav|length>1 or (page.next_page or page.previous_page) or config.repo_url %}
  <!-- Expander button -->
  <button type="button" class="navbar-toggler" data-toggle="collapse" data-target=".navbar-collapse" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon">