Buildable without flakes
Do not select an nncp-version in the overlay
Nimble compatibility
Remove git-annex wrapper

Wrapping the "git-annex" utility can cause undue confusion.
Split transfers into packets

Do not batch all transfers into a single stream. Invoke nncp-exec
for each transfer so that every transfer has its own packet. This
allows transfers to complete where call-time is limited rather
than only process transfers after all data in the batch is
received. This also allows transfers to be preëmpted by higher
priority packets.
Wrap utilities to find git-annex and nncp