Another special remote that git-annex can use is a bup repository. Bup stores large file contents in a git repository of its own, with deduplication. Combined with git-annex, you can have git on both the frontend and the backend.
Here's how to create a bup remote, and describe it.
[[!template Error: failed to process template note ]]
# git annex initremote mybup type=bup encryption=none buprepo=example.com:/big/mybup
initremote bup (bup init)
Initialized empty Git repository in /big/mybup/
ok
# git annex describe mybup "my bup repository at example.com"
describe mybup ok
Now the remote can be used like any other remote.
# git annex move my_cool_big_file --to mybup
move my_cool_big_file (to mybup...)
Receiving index from server: 1100/1100, done.
ok
Note that, unlike other remotes, bup does not really support removing content from its git repositories. This is a feature. :)
# git annex move my_cool_big_file --from mybup
move my_cool_big_file (from mybup...)
content cannot be removed from bup remote
failed
git-annex: 1 failed
See bup for details.