For git-annex to be able to clone its repo to another host, it'd be good to
have some way of pairing devices.

It could work like this:

1. Prompt for the hostname (or do avahi local machine discovery). 
2. Enable the two hosts to ssh to one-another and run git-annex shell.
   (A tricky problem, if ssh keys need to be added to do that.)
3. Push over a clone of the repository. (Using git-annex-shell?)
4. Start [[syncing]].

Also look into the method used by
<https://support.mozilla.org/en-US/kb/add-a-device-to-firefox-sync>