I always believed that side-by-side diff view is a transclusion interface.

Also, permalinks can work on top of git quite nicely https://replicated.live/blog/link

If git's pack index gets refactored slightly, it can do anything from trigram-indexed search to metadata indexing to hyperlinking both ways across repos. That is actually useful, I use it: https://replicated.live/blog/wiki

CRDT merges are a very incremental and useful upgrade for git https://replicated.live/blog/meta

Xanadu-like functionality is perfectly within reach.

We don't get what we want or what we need. Instead, we move erratically in very small, easy, local steps.