[nonameiguess]

It will have expired by now, but ClearCase is exactly what I think of whenever I see these kinds of ideas come up. It's really a handy tool but too bad almost nobody uses it or has even heard of it in the open source world since it isn't free (in any sense of the word). They were still using it at the NRO's ground processing stations as recently as six years ago. Just rsync VOBs between dev, staging, and prod environments, and checkout a particular view to install upgrades and you're guaranteed to have a totally identical environment complete with all dependencies, no containers necessary. It's really better than Git for this, too, because it can work as a distributed filesystem across many hosts at once, handles binary files perfectly well without needing extensions, uses a real database. You can version control an entire cluster of servers the same way Git version controls a single software project.

But it's 90s IBM enterprise business model to the core and the rest of the Rational product suite sucks.