From LuxRender Wiki
Git is an alternative to Mercurial or CVS. It allows you to easily store a complete copy of the repository on your local machine and maintain local changes in it while at the same time tracking the official development. A git mirror of the LuxRender CVS repository used to be available, but it is not currently synchronised with the Mercurial server. Therefore, please stick to using Mercurial for the time being
Git should be available through the package system of most Linux distributions. If not available precompiled on your system, or you want to compile it yourself, see git's homepage.
Obtaining LuxRender Through Git (not currently recommended, please use Mercurial instead)
If git is installed, you should be able to clone the LuxRender repository by issuing the following command:
git clone git://git.andersberle.com/luxrender.git
This will put the repository in the subdirectory luxrender of your current directory. This directory contains all the files from the most recent version of the LuxRender source code and a directory called .git. To learn what to do from here, see the git tutorial or git for CVS users.