When using an existing repo, copy over all of its config into the sim.
Added CommandTrustLevel.
Start at creating a git clone for a simulated repo, but it's not done
yet.
Added checks that repo names are ones that have been added to the sim.
Implemented preferred content etc setting. It does not need to parse the
expression in applySimCommand, instead that can be done when running the
sim. This keeps it pure.
But, it can't be entirely pure because of CommandAddTree. So made it
return an Annex action when necessary.
Moved makeMatcher into Annex.FileMatcher in preparation for using it,
but it's not used yet. Also moved checkPreferredContentExpression.
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.
