Hide topic text excerpt for spoilers

tildes/tildes/templates/macros/topics.jinja2

@@ -47,6 +47,15 @@
     </div>
 
     {% if topic.is_text_type and topic.get_content_metadata('excerpt') %}
+      {# warn about spoilers #}
+      {% if 'spoiler' in topic.tags %}
+        <details class="topic-text-excerpt">
+          <summary>
+            <span>Warning: this post may contain spoilers.</span>
+          </summary>
+          {{ topic.rendered_html|safe }}
+        </details>
+      {% else %}
         {# if the "excerpt" is the full text, don't wrap in <details> #}
         {% if not topic.get_content_metadata('excerpt').endswith('...') %}
           <p class="topic-text-excerpt">{{ topic.get_content_metadata('excerpt') }}</p>
@@ -63,6 +72,7 @@
           </details>
         {% endif %}
       {% endif %}
+    {% endif %}
 
     <footer class="topic-info">
       <div class="topic-info-comments">