I'm sorry but if you've been writing one of the most complex and elaborate video games in human history, you can figure git out, probably faster than it took Linus to write it (a weekend).
I'm sorry, but if your development model works fine for you and has allowed you to create a cornerstone of gaming culture and keep updating it for nearly 2 decades with a 2 person team... maybe you don't need to take advice from internet know-it-alls?