Edit: Thanks for your kind comments on disabling contributions. I'm aware of the possibility, this is just a meme.
Contributions in open source projects are great, needed and make the world a better place after all. Therefore they should be declined politely, optionally by giving a reason.
I hereby inform you that I will no longer accept contributions to this post /s.
I never understand people who don't install every free FOSS software offered to them on their PC.
Why would someone take every contribution to their FOSS project? It makes no sense to take a contribution doesn't help the project owner's vision of the project.