No question.. Git is the best practice.
If you're creating an entirely new script with no intention to merge the 2 together then make a new git repo.
If you're creating a new version of an existing script, like a beta or alpha version, then make a new branch within the same repo.
Googling git best practices you get a lot of branching strategies, commit tagging and naming conventions etc. But those are only really useful when you run a large software shop with multiple developers. If you're working alone, just find out what works for you. Github offer free private repos now and if you're looking to roll with your own selfhosted gitlab is really nice but potentially a bit overkill for a few repos.