adding open graph to head of site

_includes/head--opengraph.html

@@ -0,0 +1,38 @@
+<meta content="{{ site.title }}" property="og:site_name">
+{% if page.title %}
+  <meta content="{{ page.title }}" property="og:title">
+{% else %}
+  <meta content="{{ site.title }}" property="og:title">
+{% endif %}
+{% if page.title %}
+  <meta content="article" property="og:type">
+{% else %}
+  <meta content="website" property="og:type">
+{% endif %}
+{% if page.description %}
+  <meta content="{{ page.description }}" property="og:description">
+{% else %}
+  <meta content="{{ site.description }}" property="og:description">
+{% endif %}
+{% if page.url %}
+  <meta content="{{ site.url }}{{ page.url }}" property="og:url">
+{% endif %}
+{% if page.date %}
+  <meta content="{{ page.date | date_to_xmlschema }}" property="article:published_time">
+  <meta content="{{ site.url }}" property="article:author">
+{% endif %}
+{% if page.image %}
+  <meta content="/img/{{ page.image }}" property="og:image">
+{% else %}
+  <meta content="/img/logo-high-resolution.png" property="og:image">
+{% endif %}
+{% if page.categories %}
+  {% for category in page.categories limit:1 %}
+  <meta content="{{ category }}" property="article:section">
+  {% endfor %}
+{% endif %}
+{% if page.tags %}
+  {% for tag in page.tags %}
+  <meta content="{{ tag }}" property="article:tag">
+  {% endfor %}
+{% endif %}

_includes/head.html

@@ -9,4 +9,6 @@
   <link rel="stylesheet" href="{{ "/css/main.css" | prepend: site.baseurl }}">
   <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.baseurl | prepend: site.url }}">
   <link rel="alternate" type="application/rss+xml" title="{{ site.title }}" href="{{ "/feed.xml" | prepend: site.baseurl | prepend: site.url }}">
+
+  {% include head--opengraph.html %}
 </head>