{% macro nav(request, app=None) -%}
{% set root_items = [] %}
{% if crumb_items is defined %}
  {% set root_items=crumb_items(request=request) %}
{% endif %}
<p class="crumbs">
  {% for item in root_items %}
    <a href="{{ item.href }}">{{ item.label }}</a>
    /
  {% endfor %}
  <a href="{{ urls.path('/-/apps') }}">apps</a>
  {% if app %}
    /
    <a href="{{ urls.path(app.path) }}">{{ app.name }}</a>
  {% endif %}
</p>
{%- endmacro %}