Propellor currently needs a central git server. And it has a special-cased protocol during bootstrap that transfers the git repo over to a new host, using the ssh connection that will be used to run propellor.
This could be improved by making a git push be done whenever
propellor spin $host runs. The remote propellor runs git receive-pack;
the local one runs git send-pack.
Then there would be no need for a central git repo. Although still very useful if you have multiple propellor driven hosts and you want to just git commit and let cron sort them out.