How to forbid Git merge certain branches

Question

I need support of 3 versions of my program. Where most files are

joint (common) but several files contain different content for each version.

I'll probably use 4 branches A,B,C,D in Git.

Form example project Ice-cream:

____________________________________________________
Cup.txt: { Waffle cup } – common file for all version

Filling.txt { banana } - special file for B version
Filling.txt { strawberries } - special file for C version
Filling.txt { vanilla } - special file for D version
____________________________________________________

A - branch suitable only for global files (Cup.txt)

B,C,D - branch suitable only for Filling.txt file.

For this strategy I need allow to merge only in one direction: A => B,C,D

My question is how to forbid merging from B,C,D to A branches in Git?

Answer 1

Regarding source code, it is best to avoid complex merge strategy, and modify PrintBill in order to:

• separate content specific to client A and B
• build the right executable for client A and client B by choosing the right source

The idea is the same than the one initially written below: avoid any complex merge strategy.

Now if that kind of refactoring isn't possible, you can try and declare a merge driver , but that won't be always called (only in case of conflicts)

---

Another approach would be to avoid versioning Filling.txt (that way, no more merge strategy headache).

You can:

• version 3 different files with values for each environment
• setup a smudge script (a content filter driver declare in a .gitattributes file ) which will automatically on checkout generate, depending on the checked out branch, the right Filling.txt

Answer 2

Firstly, I don't think this is really what you want to do.

You want to forbid merging in B-specific stuff into A.

But merging general bug fixes from B to A should be fine.

So you should keep B-specific stuff in separate files.

Anyway, what you need is something like a git pre-receive hook on the "central server", which checks for and prevents additions of "banned files", I think.

But note that if you do keep B-specific stuff in separate files, you don't even need to use git branches to solve this problem. You can just use separate projects with dependencies between them.