🐛 fix(archive): group multi-sourced posts by year

Closes #251.

templates/archive.html

@@ -25,24 +25,33 @@
             {%- set_global all_posts = all_posts | concat(with=section_item.pages) -%}
         {%- endfor %}
 
-        {% for year, posts in all_posts | group_by(attribute="year") %}
-        {% if posts | length > 0 %}
-        <li>
-            <h2 class="listing-title">{{ year }}</h2>
-            <ul class="listing">
-                {% for post in posts %}
-                <li class="listing-item">
-                    <div class="post-time">
-                        <span class="date">
-                            {{ post.date | date(format="%d %b", locale=date_locale) }}
-                        </span>
-                    </div>
-                    <a href="{{ post.permalink }}" title="{{ post.title }}">{{ post.title }}</a>
-                </li>
-                {% endfor %}
-            </ul>
-        </li>
-        {% endif %}
+        {# Group posts by year. #}
+        {% set posts_by_year = all_posts | group_by(attribute="year") %}
+        {% set years = [] %}
+        {% for year, ignored in posts_by_year %}
+            {% set_global years = years | concat(with=[year]) %}
+        {% endfor %}
+
+        {# Iterate over sorted & reversed years (newest to oldest). #}
+        {% for year in years | sort | reverse %}
+            {% set posts = posts_by_year[year] %}
+            {% if posts | length > 0 %}
+            <li>
+                <h2 class="listing-title">{{ year }}</h2>
+                <ul class="listing">
+                    {% for post in posts %}
+                    <li class="listing-item">
+                        <div class="post-time">
+                            <span class="date">
+                                {{ post.date | date(format="%d %b", locale=date_locale) }}
+                            </span>
+                        </div>
+                        <a href="{{ post.permalink }}" title="{{ post.title }}">{{ post.title }}</a>
+                    </li>
+                    {% endfor %}
+                </ul>
+            </li>
+            {% endif %}
         {% endfor %}
     </ul>
 </div>