Only fire update diff base when the dot repo is scanned (#2510)

This PR fixes a bug in the firing of the UpdatedRepositories event which
caused it to flood collaboration with new messages on every file save.

Release Notes:

* Fixed a bug in repository detection that caused it to fire
over-eagerly (preview only)
4c9d24da7cMikayla Maki committed on 5/22/2023, 9:11:19 PM· committed by GitHubparents0e332b596224fa
1 file changedLine totals unavailable