repair: Add a --dry-run option
repair: Add a --dry-run option

This will just report inconsistencies it finds,
but not make changes.

Closes: #2473
Approved by: alexlarsson

flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak