{% comment %}

Include this partial in a head section to include a series of URLs for a
given property, like og:image or og:video.

You must pass the following variables:

* property: A string with the name of the property, like 'image' or 'video'.
* urls: A sequence of URL strings.  Each should include at least an absolute
  path.  This partial will fill in a scheme and host if needed.

You may also pass:

* fallback: A URL string, following the same rules as in `urls`.  This URL
  will be used if `urls` is empty.

{% endcomment %}

{% load fill_url %}
{% for url in urls %}
<meta property="og:{{ property }}" content="{{ url|fill_url:host_url }}">
{% empty %}
{% if fallback %}
<meta property="og:{{ property }}" content="{{ fallback|fill_url:host_url }}">
{% endif %}
{% endfor %}