Add "group by array" include to simplify archive pages

_pages/category-archive.html

@@ -4,24 +4,19 @@ permalink: /category-archive/
 title: "Posts by Category"
 ---
 {% include absolute-url.liquid %}
-{% capture site_categories %}{% for category in site.categories %}{{ category | first }}{% unless forloop.last %},{% endunless %}{% endfor %}{% endcapture %}
-{% assign category_list = site_categories | split:',' | sort %}
+{% include group-by-array.html collection=site.posts field='categories' %}
 
-{% for item in (0..site.categories.size) %}
-  {% unless forloop.last %}
-  {% capture category_name %}{{ category_list[item] | strip_newlines }}{% endcapture %}
-    <h3>{{ category_name }}</h3>
-    {% for post in site.categories[category_name] %}
-      {% if post.title != null %}
-        <article itemscope itemtype="http://schema.org/CreativeWork">
-          {% if post.link %}
-            <h2 class="link-post" itemprop="headline"><a href="{{ absurl }}{{ post.url }}" title="{{ post.title }}">{{ post.title }}</a> <a href="{{ post.link }}" target="_blank" title="{{ post.title }}"><i class="fa fa-link"></i></a></h2>
-          {% else %}
-            <h2 itemprop="headline"><a href="{{ absurl }}{{ post.url }}" title="{{ post.title }}">{{ post.title }}</a></h2>
-            <p itemprop="description">{{ post.excerpt | markdownify | strip_html | strip_newlines | escape_once }}</p>
-          {% endif %}
-        </article>
+{% for category in group_names %}
+  {% assign posts = group_items[forloop.index0] %}
+  <h3>{{ category }}</h3>
+  {% for post in posts %}
+    <article itemscope itemtype="http://schema.org/CreativeWork">
+      {% if post.link %}
+        <h2 class="link-post" itemprop="headline"><a href="{{ absurl }}{{ post.url }}" title="{{ post.title }}">{{ post.title }}</a> <a href="{{ post.link }}" target="_blank" title="{{ post.title }}"><i class="fa fa-link"></i></a></h2>
+      {% else %}
+        <h2 itemprop="headline"><a href="{{ absurl }}{{ post.url }}" title="{{ post.title }}">{{ post.title }}</a></h2>
+        <p itemprop="description">{{ post.excerpt | markdownify | strip_html | strip_newlines | escape_once }}</p>
       {% endif %}
-    {% endfor %}
-  {% endunless %}
+    </article>
+  {% endfor %}
 {% endfor %}