Make the header links a bit more flexible

docs/_data/nav.yml

@@ -4,15 +4,15 @@
 
 - title: GitHub
   href: https://github.com/facebook/rocksdb/
-  category: github
+  category: external
 
 - title: API (C++)
   href: https://github.com/facebook/rocksdb/tree/master/include/rocksdb
-  category: api
+  category: external
 
 - title: API (Java)
   href: https://github.com/facebook/rocksdb/tree/master/java/src/main/java/org/rocksdb
-  category: api
+  category: external
 
 - title: Support
   href: /support.html
@@ -24,4 +24,7 @@
 
 - title: Facebook
   href: https://www.facebook.com/groups/rocksdb.dev/
-  category: facebook
+  category: external
+
+# Use external for external links not associated with the paths of the current site.
+# If a category is external, site urls, for example, are not prepended to the href, etc..

docs/_includes/nav.html

@@ -11,7 +11,11 @@
           <ul>
             {% for item in site.data.nav %}
             <li class="navItem{% if page.collection == item.category or page.category == item.category %} navItemActive{% endif %}">
-              <a href="{{ item.href }}">{{ item.title }}</a>
+              {% if item.category == "external" %}
+                <a href="{{ item.href }}">{{ item.title }}</a>
+              {% else %}
+                <a href="{{ item.href | relative_url }}">{{ item.title }}</a>
+              {% endif %}
             </li>
             {% endfor %}
             {% if site.searchconfig %}