It seems geeky to host a personal blog on GitHub Pages. Suffered too much pain with other blog services as well as the huge wordpress, I have finally migrated my blog here.

GitHub Pages, however, has some limitations. Maybe for the reason of system burdun, It uses ‘–safe’ option to disable customized plugins. Option ‘–lsi’ is also ignored, which makes ‘Releated Posts’ be the latest ten posts, without considering relevance between posts. I think listing most relevant posts is essential for readers to notice other articles they may be interested. So I just googled for the problem. Here I found two webpages with potential solutions:

1. Jekyll Related Posts without Plugin
2. Jekyll “Related Posts” helper

The relevance between posts is measured by number of shared tags. It is better to re-order the related posts by relevance. Here goes my final solution (see also source of my blog):

{% if site.brute_force_lsi %}
  {% capture related %}
    {% for tag in page.tags %}
      {{ site.tags[tag] | map: "id" | join: " " }}
    {% endfor %}
  {% endcapture %}
  {% assign related = related | split: " " %}
  {% assign max_hit = 0 %}
  {% capture hits %}
    {% for post in site.posts %}
      {% assign hit = 0 %}
      {% if post.id != page.id and related contains post.id %}
        {% for id in related %}
          {% if post.id == id %}
            {% assign hit = hit | plus: 1 %}
          {% endif %}
        {% endfor %}
        {% if hit > max_hit %}
          {% assign max_hit = hit %}
        {% endif %}
      {% endif %}
      {{ hit }}
    {% endfor %}
  {% endcapture %}
  {% assign hits = hits | split: " " %}
  {% capture post_index %}
    {% assign count = 0 %}
    {% for level in (1..max_hit) reversed %}
      {% for hit in hits %}
        {% assign num = hit | minus: 0 %}
        {% if level == num %}
          {{ forloop.index0 }}
          {% assign count = count | plus: 1 %}
          {% if count >= site.related_posts_max %}{% break %}{% endif %}
        {% endif %}
      {% endfor %}
      {% if count >= site.related_posts_max %}{% break %}{% endif %}
    {% endfor %}
  {% endcapture %}
  {% assign post_index = post_index | split: " " %}
<div id="related">
  <hr />
  <h2>Related Posts</h2>
  <ul class="posts">
  {% for index in post_index %}
    {% assign num = index | minus: 0 %}
    {% assign post = site.posts[num] %}
    <li><span>{{ post.date | date: '%Y-%m-%d %H:%M' }}</span>
    - <a href="{{ post.url }}">{{ post.title }}</a></li>
  {% endfor %}
  </ul>
</div>
{% endif %}

Finally, to enable such brute force scanning for related posts, add following lines into _config.yml:

brute_force_lsi: false
related_posts_max: 6