[_cbdev]

As others have already stated, this article is a great introduction for when you'll be the only one to access the repositories, as anyone able to authenticate for that account will have access to all repos.

There are some tools that restrict access with varying levels of granularity, but if you just want to restrict access on a per-repo-per-sshkey basis, one of my projects is a simple shell script that does just that:

https://github.com/cbdevnet/fugit

It originally came to be because I've found gitolite too big to maintain for simply sharing some repositories with a few other people. It has since served me well and is used in some business applications, too.