A sftp special remote would be nice because gpg operations could be pipelined to the network transfer, not requiring the creation of a full file to disk with gpg before the network transmission, as it happens with the rsync special remote.

There should be some libraries that can handle the sftp connections and transfers. I read that even curl has support for that.

Another reason to build this is that sftp has a SFTP_FXP_STAT that can get disk free space information. "echo df | sftp user@host" exposes this, when available. Some sftp servers can be locked down so that the user can't run git-annex on them, so that could be the only way to get diskreserve working for such a remote. --Joey