ReadContent can't update the log, since it reads lazily. This part of
the P2P monad will need to be rethought.
Associated files are heavily sanitized when received from a peer;
they could be an exploit vector.
This commit was sponsored by Jochen Bartl on Patreon.
Untested, and it does not yet update transfer logs.
Verifying transferred content is modeled on git-annex-shell recvkey.
In a direct mode or annex.thin repository, content can change while it's
being transferred. So, verification is always done, even if annex.verify
would normally prevent it.
Note that a WORM or URL key could change in a way the verification
doesn't catch. That can happen in git-annex-shell recvkey too. We don't
worry about it, because those key backends don't guarantee preservation
of data. (Which is to say, I worried about it, and then convinced myself
again it was ok.)
Each worker thread needs to run in the Annex monad, but the
remote-daemon's liftAnnex can only run 1 action at a time. Used
Annex.Concurrent to deal with that.
P2P.Annex is incomplete as of yet.
