How to manage multiple similar but different projects with git?

Question

I have multiple different closed source projects based on a similar code base and every single day I need to copy changes and fixes from one to another and back.

As some of my projects are diverged too much to use git submodules and in others I don't want my clients mess with submodules and consequently peek into my work on other projects now I do that with git patch and git apply which is a tedious job.

I am about to consider a switch to git pull and git push between local repositories on my machine consequently using git cherry-pick and git merge to pick up needed changes, but if there is a better way?

Answer 1

The following are more like suggestions

Subtree merging

Stitching together repositories

I'm really interested also in this and I'll come with an update if I get to any definitive answer.