[pxc]

The Open Build Service and its version control tool, osc, offer some ability to fork a package from an upstream repo and still track upstream changes. It's not as elegant or convenient as Nix, but it is pretty cool. OBS supports packages for a ton of distros. It's essentially patch based, but targeting different distros (of the same package type) and different architectures can sometimes be without changing the source packages at all.

It might be fun to compare their approaches to solving this ejection problem. Nix's is much nicer to use and requires basically no infrastructure, of course.