Update related posts section to show posts with similar tags

Author: Edoardo Holzl

_layouts/post.html

@@ -22,16 +22,32 @@ <h1 class="post-title">{{ page.title }}</h1>
 <div class="related">
   <h2>Related Posts</h2>
   <ul class="related-posts">
-    {% for post in site.related_posts limit:3 %}
-      <li>
-        <h3>
-          <a href="{{ post.url }}">
-            {{ post.title }}
-            <small>{{ post.date | date_to_string }}</small>
-          </a>
-        </h3>
-      </li>
+    {% assign hasSimilar = '' %}
+    {% for post in site.related_posts %}
+        {% assign postHasSimilar = false %}
+        {% for tag in post.tags %}
+            {% for thisTag in page.tags %}
+                {% if postHasSimilar == false and hasSimilar.size < 6 and post != page and tag == thisTag %}
+                    {% if hasSimilar.size == 0 %}
+                      <h4>Similar Posts</h4>
+                      <ul>
+                    {% endif %}
+                    <li class="relatedPost">
+                        <a href="{{ site.url }}{{ post.url }}">{{ post.title }}
+                        {% if post.series %}
+                            (Series: {{ post.series }})
+                        {% endif %}
+                        </a>
+                    </li>
+                    {% capture hasSimilar %}{{ hasSimilar }}*{% endcapture %}
+                    {% assign postHasSimilar = true %}
+                {% endif %}
+            {% endfor %}
+        {% endfor %}
     {% endfor %}
+    {% if hasSimilar.size > 0 %}
+        </ul>
+    {% endif %}
   </ul>
 </div>