Use canonical URL for Disqus, fixes #236

.themes/classic/source/_includes/disqus.html

@@ -1,13 +1,12 @@
 {% comment %} Load script if disquss comments are enabled and `page.comments` is either empty (index) or set to true {% endcomment %}
 {% if site.disqus_short_name and page.comments != false %}
 <script type="text/javascript">
-    
       var disqus_shortname = '{{ site.disqus_short_name }}';
       {% if page.comments == true %}
         {% comment %} `page.comments` can be only be set to true on pages/posts, so we embed the comments here. {% endcomment %}
         // var disqus_developer = 1;
-        var disqus_identifier = '{{ site.url }}{{ page.url }}';
-        var disqus_url = '{{ site.url }}{{ page.url }}';
+        var disqus_identifier = '{{ canonical }}';
+        var disqus_url = '{{ canonical }}';
         var disqus_script = 'embed.js';
       {% else %}
         {% comment %} As `page.comments` is empty, we must be on the index page. {% endcomment %}

.themes/classic/source/_includes/head.html

@@ -16,7 +16,7 @@
   <meta name="MobileOptimized" content="320">
   <meta name="viewport" content="width=device-width, initial-scale=1">
 
-  {% capture canonical %}{{ site.url }}{% if site.permalink contains '.html' %}{{ page.url }}{% else %}{{ page.url | remove:'index.html' }}{% endif %}{% endcapture %}
+  {% capture canonical %}{{ site.url }}{% if site.permalink contains '.html' %}{{ page.url }}{% else %}{{ page.url | remove:'index.html' | strip_slash }}{% endif %}{% endcapture %}
   <link rel="canonical" href="{{ canonical }}">
   <link href="{{ root_url }}/favicon.png" rel="icon">
   <link href="{{ root_url }}/stylesheets/screen.css" media="screen, projection" rel="stylesheet" type="text/css">