Finished the refactoring that I had started on Thursday. This was only a partial success, because it didn't result in the speedup to -J that I had hoped for. The slow start with -J turns out to not be caused by concurrency overhead at all, but a bug, rsync and gcrypt special remotes make -J slow.

What was successful is that I got rid of the oldest implementation wart in git-annex, the implicitMessages state. And, I made progress toward separately parallizing checksum verification.

This refactoring is still cooking in the starting branch and will be merged after the next release.