So how does it work for Openstreetmap? I mean git is not very good at handling large repositories, fsck and all that takes ages. So what performance do you get with an small geographical area?
OpenStreetMap has it's own versioning mechanisms (and a fairly specific-to-OSM data model) and Kart isn't really designed to work with OSM data as such. Kart adds version control to the GIS data that planners, academics, architects, civil engineers, etc, use day-to-day. There's a lot of data out there!
"Large" is relative, but Kart works well with quite big vector datasets for these typical use cases. For example, we're regularly working with datasets that have over 2 million features, with a decade of weekly data changes.
Kart includes some feautres specifically for working with small geographic areas. We can spatially filtering cloned data so you're working with a small subset of a much larger dataset, but you still retain the abilityt commit/merge/push to the source repo.