Using `balanced` or similar preferred content expressions makes files be
spread amoung repositories in a group, but does not take numcopies into
account. Could this be made to support numcopies?

The number of nodes to store each file on can be specified
(`balanced=foo:N`). That is a separate number than numcopies. When
different files have different numcopies, a single number there is not
always useful. (Although it may be that someone always wants each file in
the cluster to have say, 3 copies, regardless of numcopies.)

Could `balanced=foo:lackingcopies` just make enough nodes want copies to
satisfy numcopies? (Assuming there are enough nodes.)

That would not be the same as using `balanced=foo or lackingcopies=1`,
because that makes every node want every file until numcopies is satisfied.
So that does not evenly balance files amoung nodes. Eg, if `git-annex
sync` is syncing with 3 nodes and happens to always try sending to A first,
A would get every file, and B and C would not get any files with that
preferred content expression.

> Implemented! [[done]] --[[Joey]]
