It probably depends on exactly what and how complex your “transformation” is. You definitely can do lots of automation with $ git itself in terms of committing, merging, opening PRs on GitHub via $ hub, etc.

Another idea is if you can refactor the common bits into a shared standard library, for instance the design pattern is something like a system with a bunch of plugins, then most of the plugin repos become very tiny. Ideally you’d also have some sort of infrastructure automation around deployment.