Without actually simulating cluster implementation at all. Instead, only
the essential fact that cluster gateways know what changes they have
made to each node of a cluster. That is enough for sims like
sizebalanced_cluster.
Noticed that it was quite slow compared with things like action
sendwanted. Guessed that the slowdown is largely due to every step
doing a simulated git pull/push.
So, rather than always doing a pull/push, only do those when no actions
are found without doing a pull/push.
This does mean that step will sometimes experience a split brain
situation, but that seems like a good thing? Because step ought to
explore as many possible scenarios as it reasonably can.
Not tested yet. This emulates the same checking that is done when
dropping. Note that when dropping from a special remote it is not able
to make a locked copy.
The generator doesn't emit the best possible connect commands,
but it does output something valid. Eg, an input like:
connect A <-> B <-> C <-> D
becomes:
connect A <-> B <-> C
connect C <-> D
Also:
connect A -> B <- C
becomes:
connect A -> B
connect C -> B
Which could be improved.
Also disconnect commands are not prettified at all, but probably there's
no reason to.
