The branching policy of a ROS package as well as a pure Python package is determined by the maintainer.
For ROS packages there are two common options:
* creating separate branches for each distro
* keeping a single master from where a release is made into all distros
* (or sometimes even a mix: separate branches for Fuerte and Groovy but Hydro uses Groovy since there are no changes between those two)
For ROS distro independent releases there is commonly only one master branch.
rosdoc_lite is a mixture of both.
It needs two different branches for Fuerte (old logic) and Groovy/Hydro (new logic).
The buildfarm checks out the respective branch and uses rosdoc_lite from source (as far as I know).
Adding the Groovy branch to the Hydro doc.yaml is the right way for this.
Just creating a Hydro branch for the sake of have that name creates unnecessary overhead.
I am not sure why rosdoc_lite is at all released as a ROS Debian package.
That decision backdates to the time where Eitan / Wim worked on these tools.
With the EOL of Fuerte coming soon we might want to consider removing the ROS distro specific package, unlisting it from the distro files including doc.
We could than either release it as a ROS distro agnostic pure Python package and deploy that on the farm using puppet or just keep it as it is and checkout the repo on the farm.