I have a not super unique situation in which I have multiple copies of the same code base for different clients. They all have some version of a master code base, however they are all different in some manner.

In addition, it is not possible to simply version the software and roll it out to each client in version increments. Instead, features and bug fixes need to be pushed back and forth in a cherry picked manner.

I haven't found any tool capable of doing this, so I ended up writing a power shell script to help me manage it.
https://jeremeguenther.blogspot.com/2020/03/syncing-similar-code-base-between.html