docs: major overhaul (#19395)

_includes/head.html

@@ -7,28 +7,20 @@
     <!-- debug root:{% include link.html url="/debug-path" %} -->
 
     <link rel="icon" type="image/png" href="{% include link.html url=site.favicon %}" />
-    {% if layout.common-css %}
-        {% for css in layout.common-css %}
-    <link rel="stylesheet" href="{% include link.html url=css %}" />
-        {% endfor %}
-    {% endif %}
+{% for x in layout.common-css %}{% capture target %}{% include link.html url=x %}{% endcapture %}
+    <link rel="stylesheet" href="{{ target |strip }}" />
+{% endfor %}
 
-    {% if page.css %}
-        {% for css in page.css %}
-    <link rel="stylesheet" href="{% include link.html url=css %}" />
-        {% endfor %}
-    {% endif %}
+{% for x in page.css %}{% capture target %}{% include link.html url=x %}{% endcapture %}
+    <link rel="stylesheet" href="{{ target |strip }}" />
+{% endfor %}
 
-    {% if layout.common-js %}
-        {% for js in layout.common-js %}
-    <script src="{% include link.html url=js %}"></script>
-        {% endfor %}
-    {% endif %}
+{% for x in layout.common-js %}{% capture target %}{% include link.html url=x %}{% endcapture %}
+    <script src="{{ target | strip }}"></script>
+{% endfor %}
+
+{% for x in page.js %}{% capture target %}{% include link.html url=x %}{% endcapture %}
+    <script src="{{ target | strip }}"></script>
+{% endfor %}
   
-    {% if page.js %}
-        {% for js in page.js %}
-    <script src="{% include link.html url=js %}"></script>
-        {% endfor %}
-    {% endif %}
-
-</head>
+</head>

_includes/link.html

@@ -1,2 +1 @@
-{% capture root %}{% if page.root %}{{ page.root }}{% else %}{{ site.default_root }}{% endif %}{% endcapture %}
-{{ include.url | remove: ".html" | prepend: root | replace: '//', '/' }}
+{% if page.root %}{% assign root=page.root %}{% else %}{% assign root=site.default_root %}{% endif %}{{ include.url | remove: ".html" | prepend: root | replace: '//', '/' }}