> I suppose its harder to query git servers for whether they are storing a user's repository.

You should be able to query a server for "all repos signed by public key X" the same way you can query a nostr relay for "all events signed by public key X".

But on nostr relays can just store your events without your involvement. A relay can mirror another one just by pulling events off of it.

Your git server idea requires going back to the maintainer for each new server, the maintainer has to approve each new git server with a signed event that needs to be broadcast. So there's a bottleneck there.