Currently, some issues impede the use of export remotes: (1) they're untrusted, except for versioned ones -- and from those keys cannot be dropped; (2) using them is different than using normal remotes: one can't just copy or move keys to them, one has to first make a tree-ish. Maybe this could be fixed, as follows. To copy a key to an export remote, if the key is not yet present in it, put it under .keys/aaa/bbb/keyname on the remote. That is, take the tree-ish currently on the remote, merge .keys/aaa/bbb/keyname with it, and put that on the remote. To drop a key from an external remote, take the tree-ish currently on the remote, drop all instances of the key from it, and push the changed tree-ish to the remote. To git-annex-export add an option --add , which will add the tree-ish to the tree-ish currently on the remote, without losing any keys currently on the remote: take the tree-ish currently on the remote; overlay on it the treeish being exported; for any files that would be overwritten, if no copies of that key would be left, move it to .keys/aaa/bbb/keyname in the tree-ish that is then pushed to the remote.
