Not yet added anything to the protocol to get a list of remote config
fields; any fields will be accepted and are available for the external
remote to use as before.
There is one minor behavior change.. Before, GETCONFIG could be passed a
field such as type, externaltype, encryption, etc, and would get the
value of that. Now, GETCONFIG only works on fields that don't have a
defined meaning to git-annex, so are passed through to the external
remote. This seems unlikely to affect any external special remotes in
practice.