Klaus pointed out that there are two problems that keep
git-annex from being used on USB keys, that would typically
be VFAT formatted:

- Use of symlinks, which VFAT does not support. Very hard to fix.
  Instead, just use [[/bare_repositories]] on the key,
  they're supported now.
- Use of ":" in filenames of object files, also not supported.
  Could easily be fixed by reorganizing the object directory.

[[Done]]; in annex.version 2 repos, colons are entirely avoided in
filenames. So a bare git clone can be put on VFAT, and git-annex
used to move stuff --to and --from it, for sneakernet.