git-annex test could run git-annex testremote with a single directory
remote. This would both find bugs in testremote, and probably generally
bugs involving special remote operations, of course especially with the
directory remote.

To avoid confusing output, running testremote itself is not ideal,
instead, it would be great to have Command.TestRemote export a TestTree,
that could then be added to the test suite's TestTree. 

(See [[bugs/testremote_failures_starting_with_aeca7c220]])

--[[Joey]]

> [[done]] --[[Joey]]
