External daemons like rpm-ostree want push notification any time a
change is made by an external entity. inotify provides notification,
but a problem is there's no easy way to monitor all of the refs.
In the past, there has been discussion of opt-in recursive timestamps:
https://lkml.org/lkml/2013/4/5/307
But in today's world, let's just bump the mtime on the repo itself, as
a central inotify point.
Closes: https://github.com/GNOME/ostree/pull/111
Colin Walters
efcdf4c3f8