git save requires existing repository

[Dirk Hohndel]

Linus,

can you remind me of the rationale why you did this?

I obviously didn't get around writing a better UI for git saves (huge
surprise), but when I just looked through the code to help Miika figure
out how to test it, I realized that I thought we talked about Subsurface
simply creating a new repository if there isn't onw - but then I can't
remember why we aren't doing that.

Thanks

/D