Hi Archers,
EDIT: I've now uploaded "nexuiz-svn-light", which skips over a GB of svn versioning info to provide a smaller download and local source directory. This still updates the source every time it's run and thus creates the latest version. If you need the svn versioning info (for commits), look for the "nexuiz-svn" package on the AUR.
If you install with yaourt, do not delete the sources. If yaourt does not let you reuse the sources, don't use it. Just download the package from AUR and run makepkg in the untarred build directory.
I've created (and painfully tested) an svn package for Arch (nexuiz-svn-light):
http://aur.archlinux.org/packages.php?ID=23011
When run, it will pull the latest checkout and build an installable package similar to the one in the community repo. Every time you run "makepkg" on it (or use yaourt), you will get the bleeding-edge installable package.
Do NOT use this for a single build then throw away the build directory. Keep the build directory to avoid having to download the entire svn repo again.
Like the community repo package, it includes desktop files. The path binaries will be
nexuiz-glx-svn
nexuiz-sdl-svn
nexuiz-dedicate-svn
It can happily live alongside the community package too.
Anyway, getting the latest svn version can't get much easier than this... now build it the Arch way and go find some bugs.
I check the Arch forum more frequently than this one at the moment. If you have questions, you're better off posting on the AUR or catching me on IRC/in game if you need a quick reply.
*edit*
p.s. There's also an svn client package, if you only want that. This one contains the client and the data (and fteqcc for that matter).