That's begging the question: git-upload-pack takes a ref and a commit ID, and returns a pack of objects to the requester to do as they like. I wouldn't call it a merge, but a set of operational transformation actions to be added to the requester's repo. It may not even examine the DAG at all, since it's possible to save those packs as 'bundles'!

My point is, if you focus on the implementation differences, my understanding won't increase because we don't have the same mental model of how git works under the hood.