perf(core): speed up the Jekyll build times (#1163)

Refactor `_includes/related-posts.html`

_includes/related-posts.html

@@ -1,7 +1,4 @@
-<!--
-  Recommend the other 3 posts according to the tags and categories of the current post,
-  if the number is not enough, use the other latest posts to supplement.
--->
+<!-- Recommend the other 3 posts according to the tags and categories of the current post. -->
 
 <!-- The total size of related posts -->
 {% assign TOTAL_SIZE = 3 %}
@@ -14,11 +11,21 @@
 
 {% assign SEPARATOR = ':' %}
 
+{% assign match_posts = '' | split: '' %}
+
+{% for category in page.categories %}
+  {% assign match_posts = match_posts | push: site.categories[category] | uniq %}
+{% endfor %}
+
+{% for tag in page.tags %}
+  {% assign match_posts = match_posts | push: site.tags[tag] | uniq %}
+{% endfor %}
+
+{% assign last_index = match_posts.size | minus: 1 %}
 {% assign score_list = '' | split: '' %}
-{% assign last_index = site.posts.size | minus: 1 %}
 
 {% for i in (0..last_index) %}
-  {% assign post = site.posts[i] %}
+  {% assign post = match_posts[i] %}
 
   {% if post.url == page.url %}
     {% continue %}
@@ -54,34 +61,20 @@
   {% endfor %}
 {% endif %}
 
-<!-- Fill with the other newlest posts -->
-{% assign less = TOTAL_SIZE | minus: index_list.size %}
-
-{% if less > 0 %}
-  {% for i in (0..last_index) %}
-    {% assign post = site.posts[i] %}
-    {% if post.url != page.url %}
-      {% capture cur_index %}{{ i }}{% endcapture %}
-      {% unless index_list contains cur_index %}
-        {% assign index_list = index_list | push: cur_index %}
-        {% assign less = less | minus: 1 %}
-        {% if less <= 0 %}
-          {% break %}
-        {% endif %}
-      {% endunless %}
-    {% endif %}
-  {% endfor %}
-{% endif %}
+{% assign relate_posts = '' | split: '' %}
+
+{% for index in index_list %}
+  {% assign i = index | to_integer %}
+  {% assign relate_posts = relate_posts | push: match_posts[i] %}
+{% endfor %}
 
-{% if index_list.size > 0 %}
+{% if relate_posts.size > 0 %}
   <div id="related-posts" class="mb-2 mb-sm-4">
     <h3 class="pt-2 mb-4 ms-1" data-toc-skip>
       {{ site.data.locales[include.lang].post.relate_posts }}
     </h3>
     <div class="row row-cols-1 row-cols-md-2 row-cols-xl-3 g-4 mb-4">
-      {% for entry in index_list %}
-        {% assign index = entry | plus: 0 %}
-        {% assign post = site.posts[index] %}
+      {% for post in relate_posts %}
         <div class="col">
           <a href="{{ post.url | relative_url }}" class="card post-preview h-100">
             <div class="card-body">