Depends on the project. New features and things do get separate branches that eventually get merged in once tested thoroughly, especially for website developmen

Depends on the project. New features and things do get separate branches that eventually get merged in once tested thoroughly, especially for website development projects. But it definitely depends. A website usually benefits from feature/bugfix branches more than a game or mod does, since the latter usually has the parts so atomised that your changes to one would have basically zero effect on any others.