At Elementary we've adopted `latest` as it tracks nicely with the bleeding-edge tag for Docker containers which we don't have control over. This way, when we build/deploy containers off of the `latest` branch there's an equivalent tag on our DockerHub repos.
Hmm, not sure about "latest", as almost always, the master/primary/whatever branch is not actually the latest code, but the latest "production ready" code.
https://github.com/elementary-robotics/atom