Is there a way to synchronize changes between two or more of the same files?

Question

IDE

I work in phpstorm, ubuntu.
Let's say I have a project that includes 2 subproject folders, these subprojects are generally similar, only a few files differ. How can I synchronize changes between the same files of both subprojects, so that when a file in one subproject changes, the same file in another subproject automatically changes?
The plugin can be some kind or softinka.

Answer 1

Will hardlink/symlink help?

Answer 2

You can not use any additional software, but simply leave only 1 copy of these files and make them common to both projects, and at the end of development, again divide 1 project into two branches.

Answer 3

include