Note that I tried an evil remote that lists ImportLocations with
../../../ in them and indeed this resulted in git blowing up and the
import failing, and not writing outside the repo.
Had to add two more API calls to override export APIs that are not safe
for use in combination with import.
It's unfortunate that removeExportDirectory is documented to be allowed
to remove non-empty directories. I'm not entirely sure why it's that
way, my best guess is it was intended to make it easy to implement with
just rm -rf.
