I am actively working on the general source install instructions:
http://ros.org/wiki/groovy/Installation/Source/New
Currently they are targeted at Ubuntu and have some problems still, but the important thing is that this page tells you how you can use wstool to get all of the packages for a given variant (like desktop or desktop-full) and how you can use the latest rosdep to fetch all dependencies (even on OS X Homebrew). I'll summarize those here:
$ mkdir ~/groovy_catkin
$ cd ~/groovy_catkin
$ wstool init src http://packages.ros.org/web/rosinstall/generate/raw/groovy/desktop
$ rosdep install --from-paths src --ignore-src --rosdistro groovy -y
$ ./src/catkin/bin/catkin_make
$ ./src/catkin/bin/catkin_make install
That should have fetched, resolved, built, and installed all of the wet (catkin) packages that make up the desktop variant into the ~/groovy_catkin/install folder. You can then source the setup.bash in that folder to source your newly built groovy space.
I have built and installed the desktop variant on OS X using Homebrew last week. But there potentially remain some snags which have been fixed but not released yet. I am currently working my way through the desktop-full variant fixing things as I go (on Ubuntu and OS X).
The thing still lacking from the instructions I linked is the part where you download and build/use the dry (rosbuild) parts of the variant. I hope to have that part soon (it is not hard, I just haven't finished testing the wet stuff yet).
