P2P protocol version 1 adds VALID|INVALID after DATA; INVALID means the
file was detected to change content while it was being sent and so we
may not have received the valid content of the file.
Added new MustVerify constructor for Verification, which forces
verification even when annex.verify=false etc. This is used when INVALID
and in protocol version 0.
As well as changing git-annex-shell p2psdio, this makes git-annex tor
remotes always force verification, since they don't yet use protocol
version 1. Previously, annex.verify=false could skip verification when
using tor remotes, and let bad data into the repository.
This commit was sponsored by Jack Hill on Patreon.
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