Probably a good idea for freezing, but especially I hope this fixes a
problem with git-annex sim run that caused it to sometimes crash in
removeDirectoryRecursive with directory not empty, presumably because a
thread was writing there at the same time.
Had to add Read instances to Key and NumCopies and some other similar
types. I only expect to use those in serializing a sim. Of course, this
risks that implementation changes break reading old data. For a sim,
that would not be a big problem.
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.
Have most of the sim command handler, but to keep it pure while implementing
the rest will need some refactoring.
It seems likely that running the simulation itself will not be able to be
entirely pure. Preferred content evaluation runs in Annex after all.
Note that the somewhat awkward randomWords is because the i386ancient
build depends on a version of random too old to support generating a
random ByteString on its own.
