Something to consider.

kpt has a nice scheme for versioning packages using tags:
https://kpt.dev/book/03-packages/08-publishing-a-package

However, I'd also like to version variants generated from a cloned package. They specify the version of the upstream package they were derived from, in upstream info, but not their own version.

I tried to use an annotation on the Kptfile to track versions, but without special merge handling, it frequently gets clobbered or conflicts on updates by changes to the version annotation in the upstream package. So, at present, I need to choose a different version annotation key for each level of the derivation tree.

kpt pkg get is like git clone. kpt is missing something like github fork. In the case of versioning, it would give the variant its own version number independent of the upstream package.

This could be added in a layer on top of kpt, similar to how github is a layer on top of git, but it may be worth thinking about a first-class variant-spawning model.