Helpful info for me: VersionPress is a free and open source version control plugin for WordPress built on Git. We increase major version numbers quite rapidly, e.g., VersionPress is at 3.0 at the time of writing this, but that does not mean it is production-ready.
We try to be very clear about the project status. We would love it to be magically stable soon but unfortunately, there are no shortcuts. Relational databases and (sometimes) crazily coded WordPress plugins do not fit well into the version control workflows, but we're already quite far in terms of the core technology and I'm confident WordPress will be a fully versioned platform one day.