landing-page/_includes/socialcard.html

<!-- set key defaults -->
<meta name="twitter:card" content="summary">

{% if site.app.app_twitter %}
<meta name="twitter:site" content="{{ site.app.app_twitter }}">
{% endif %}
{% if site.app.creator_twitter %}
<meta name="twitter:creator" content="{{ site.app.creator_twitter }}">
{% endif %}

<meta name="twitter:title" content="{{ site.app.name }}">
<meta content="{{ site.app.name }}" property="og:title">
<meta content="website" property="og:type">

{% if site.marketing_header %}
<meta name="twitter:description" content="{{ site.marketing_header }}">
<meta content="{{ site.marketing_header }}" property="og:description">
{% endif %}

<meta name="twitter:url" content="{{ site.url }}">
<meta content="{{ site.url }}" property="og:url">

<!-- set image -->

{% if site.app.social_image %}
<meta property="og:image" content="{{ site.app.social_image | prepend: site.url }}" />
{% else %}
<meta property="og:image" content="{{ site.app.icon | prepend: site.url }}" />
{% endif %}