Normalize auto {{ post.excerpts }}

- When excerpt: isn't set in a post's YAML Front Matter fallback to Jekyll's auto excerpts
- Strip HTML from auto excerpts and MathJax code with Liquid filters applied to post listings (index.html, /blog/, /articles/)

_posts/blog/2014-08-08-hello-world.md

@@ -3,7 +3,7 @@ layout: post
 title: "Hello World"
 modified:
 categories: blog
-excerpt: ""
+excerpt:
 tags: []
 image:
   feature:

_posts/blog/2015-08-10-mathjax-example.md

@@ -3,7 +3,7 @@ layout: post
 title: "MathJax Example"
 modified:
 categories: blog
-excerpt: ""
+excerpt:
 tags: []
 image:
   feature:

articles/index.md

@@ -7,6 +7,6 @@ search_omit: true
 
 <ul class="post-list">
 {% for post in site.categories.articles %} 
-  <li><article><a href="{{ site.url }}{{ post.url }}">{{ post.title }} <span class="entry-date"><time datetime="{{ post.date | date_to_xmlschema }}">{{ post.date | date: "%B %d, %Y" }}</time></span>{% if post.excerpt %} <span class="excerpt">{{ post.excerpt }}</span>{% endif %}</a></article></li>
+  <li><article><a href="{{ site.url }}{{ post.url }}">{{ post.title }} <span class="entry-date"><time datetime="{{ post.date | date_to_xmlschema }}">{{ post.date | date: "%B %d, %Y" }}</time></span>{% if post.excerpt %} <span class="excerpt">{{ post.excerpt | remove: '\[ ... \]' | remove: '\( ... \)' | markdownify | strip_html | strip_newlines | escape_once }}</span>{% endif %}</a></article></li>
 {% endfor %}
 </ul>

blog/index.md

@@ -7,6 +7,6 @@ search_omit: true
 
 <ul class="post-list">
 {% for post in site.categories.blog %} 
-  <li><article><a href="{{ site.url }}{{ post.url }}">{{ post.title }} <span class="entry-date"><time datetime="{{ post.date | date_to_xmlschema }}">{{ post.date | date: "%B %d, %Y" }}</time></span>{% if post.excerpt %} <span class="excerpt">{{ post.excerpt }}</span>{% endif %}</a></article></li>
+  <li><article><a href="{{ site.url }}{{ post.url }}">{{ post.title }} <span class="entry-date"><time datetime="{{ post.date | date_to_xmlschema }}">{{ post.date | date: "%B %d, %Y" }}</time></span>{% if post.excerpt %} <span class="excerpt">{{ post.excerpt | remove: '\[ ... \]' | remove: '\( ... \)' | markdownify | strip_html | strip_newlines | escape_once }}</span>{% endif %}</a></article></li>
 {% endfor %}
 </ul>

index.html

@@ -6,7 +6,7 @@
 ---
 
 <ul class="post-list">
-{% for post in site.posts limit:10 %} 
-  <li><article><a href="{{ site.url }}{{ post.url }}">{{ post.title }} <span class="entry-date"><time datetime="{{ post.date | date_to_xmlschema }}">{{ post.date | date: "%B %d, %Y" }}</time></span>{% if post.excerpt %} <span class="excerpt">{{ post.excerpt }}</span>{% endif %}</a></article></li>
+{% for post in site.posts limit:10 %}
+  <li><article><a href="{{ site.url }}{{ post.url }}">{{ post.title }} <span class="entry-date"><time datetime="{{ post.date | date_to_xmlschema }}">{{ post.date | date: "%B %d, %Y" }}</time></span>{% if post.excerpt %} <span class="excerpt">{{ post.excerpt | remove: '\[ ... \]' | remove: '\( ... \)' | markdownify | strip_html | strip_newlines | escape_once }}</span>{% endif %}</a></article></li>
 {% endfor %}
-</ul>
+</ul>