not sure how lightweight any of these are, but https://gitolite.com/gitolite/ just needs git and ssh deployed. And it works like a charm.
for anything even just sharing with friends or whatnot i won't recommend it though, people do love their web-UI and having to explicitly give someone access can turn off people already.
The lack of anonymous public access is often a deal-breaker though.
But gitolite is so easy to setup & maintain, it's not a big difference and for r/w-access management within teams, it's priceless.
I guess one could even hack anonymous access with "PermitEmptyPasswords yes" and "AuthenticationMethods none"
Or maybe you can write a shell that runs a gitolite-shell command is its arguments are not already gitolite-shell?