This adds a new `doctor` check: `fix-push-mirrors-without-git-remote`. The new check looks for push mirrors that do not have their remotes configured in git. If automatic fixing is enabled, it will remove these push mirrors from the database.
The check is not run by default, and thus, must be invoked manually. It should be usable in a half-migrated state, too, and as such, fixes#1800.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/1853
Co-authored-by: Gergely Nagy <forgejo@gergo.csillger.hu>
Co-committed-by: Gergely Nagy <forgejo@gergo.csillger.hu>
(cherry picked from commit 9038e07ef3)
