Ask HN: Free/Pro/Enterprise build management

I’ve inherited 3 separate git repos for an Enterprise, Professional and free version of a WordPress plugin. The free version has a subset of pro functionality which has a subset of the enterprise version. Generally, changes in one version need to be reflected in the other 2 so I’m looking for a DRYer solution.

I imagine it’s not wise to deliver all the enterprise code with feature turned off to the free users, so I’m investigating a solution for building the versions with only the relevant code for that specific project.

The different scenarios I’ve come across that I need to manage are

1. A file exists only in the enterprise version, but does not need to be in pro or free version 2. A file exists in the enterprise and pro version, but does not need to be in free version 3. A file exists in all 3 versions, but is not the same (eg the readme file must have different information)

Right now I’m just hacking the build process together with Rake and a list of files. It seems like this problem has probably been solved before though. So HN, have you encounter this, are you aware of any tooling for this, or do you have advice about how to solve this.

Thanks