When hosting a repository, we currently have a heuristic that tries to detect when you're doing an initial import: if you push more than 7 commits to an empty repository, it counts as an import and we disable mail/feed/etc.
Do something similar for observed repositories: if the repository is empty and we discover more than 7 commits, switch to import mode until we catch up.
This should align behavior with user expectation more often when juggling hosted vs imported repositories.