Simplify image assigns

_includes/entry.html

@@ -10,11 +10,7 @@
       <a href="{{ post.url | relative_url }}" rel="bookmark">{{ title }}</a>
     </h3>
     {% if post.image.thumbnail %}
-      {% assign entry_image = post.image.thumbnail %}
-      {% unless entry_image contains '://' %}
-        {% assign entry_image = entry_image | relative_url %}
-      {% endunless %}
-      {% assign entry_image = entry_image | escape %}
+      {% assign entry_image = post.image.thumbnail | relative_url | escape %}
       <img class="entry-image u-photo" src="{{ entry_image }}" alt="">
     {% endif %}
   </header>

_includes/masthead.html

@@ -1,8 +1,4 @@
-{% if site.logo contains '://' %}
-  {% assign site_logo = site.logo %}
-{% else %}
 {% assign site_logo = site.logo | relative_url %}
-{% endif %}
 
 <header id="masthead">
   <div class="inner">

_includes/page-intro.html

@@ -1,10 +1,6 @@
 <header class="intro">
   {% if page.image %}
-    {% assign intro_image = page.image.path | default: page.image %}
-    {% unless intro_image contains '://' %}
-      {% assign intro_image = intro_image | relative_url %}
-    {% endunless %}
-    {% assign intro_image = intro_image | escape %}
+    {% assign intro_image = page.image.path | default: page.image | relative_url | escape %}
     <div class="intro-image">
       <img src="{{ intro_image }}" alt="{{ page.title }}">
     </div>