By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Add 'bevel migrate' and run it at home-manager activation
The bevel database schema was only ever created as a side effect of running
some 'bevel' subcommand, so on a machine that had never had one run,
bevel-gather could not record anything and 'bevel sync' had nothing to sync.
'bevel migrate' takes the exclusive database lock and applies the migrations,
without doing anything else. The home-manager module runs it both from an
activation script and from a 'bevel-migrate' user service that 'bevel-sync' is
ordered after. The activation script is what actually closes the hole: the
user's systemd instance is not running while home-manager activates on a
machine nobody has logged into yet ('User systemd daemon not running.
Skipping reload.'), so the service alone does not run at that point.