<pre>
git clone git://git.xonotic.org/xonotic/xonotic.git
cd xonotic
-./all update
+./all update -l best
</pre>
The git:// protocol uses port 9418, which may be a problem if you're behind a strict firewall. You may instead use the clone url http://git.xonotic.org/xonotic/xonotic.git however using the git protocol directly is preferred for performance reasons.