How to organize a repository for a project with multiple permanent branches?

Question

git

Faced the problem of organizing a repository for one web project. The bottom line is this: there is a certain core of the project, based on the cut CodeIgniter framework. Based on this core, there are three (and more in the future) custom branches that are developed in parallel, for different customers.
The core is being actively developed, and these improvements should fall into all branches. Branches are also being actively developed.
The problem is that branch-specific modules can be scattered throughout the kernel directory structure. In addition, there are configuration files that exist both in the core and in the branches, and naturally different everywhere.
Now the question of placing this economy in the repository has become acute.
I must say right away that I have little experience with git, I used to use SVN. But as I understand it, git can be used in this case in two ways:
1. One repository. Kernel in master branch. Custom branches in separate branches. After the changes in master - merge to all branches, which will probably have to be messed with manually.
2. Submodules. Removing the kernel to the module. But how to do this if the core folders overlap with the branch folders is completely incomprehensible.
Please tell me the best practice for this situation, I do not think that it is unique. Perhaps the answer is not in git?

Answer 1

if I understand correctly, then you need to create 4 repositories. the first will be your kernel. and in 3 others actually projects for "different customers". and in these 3 the first repository will be connected via git submodule https://git-scm.com/book/en/v1/%D0%98%D0%BD%D1%81%...