Done:
* implement autosnapper that asserts interval between snapshots
* implement pruner
* job pull: pulling + pruning
* job source: autosnapping + serving
TODO
* job source: pruning
* job local: everything
* fatal errors such as serve that cannot bind socket must be more
visible
* couldn't things that need a snapshotprefix just use a interface
Prefixer() instead? then we could have prefixsnapshotfilter and not
duplicate it every time...
* either go full context.Context or not at all...? just wait because
community climate around it isn't that great and we only need it for
cancellation? roll our own?
Don't use jobrun for daemon, just call JobDo() once, the job must
organize stuff itself.
Sacrifice all the oneshot commands, they will be reintroduced as
client-calls to the daemon.
