How to block a merge with a branch?

Question

git

There is a repository. It has master, dev and other branches. But there is a "demo" branch. In this branch, the inoperable version of the program is intended for presentations and so on. I would like to have foolproofing, so that from any branch you can transfer changes to the "demo" branch, but block any attempt to transfer changes from the "demo" branch to any other.

Answer 1

Too difficult and costly. Just move the demo project to a separate repository.
If you really want to try it, read git hooks.