Not sure if this is a bug or a feature request, but calckey can only be used while inside a git repository (though the specified file can be anywhere).

Can this be changed so it can be run from anywhere?

    ~$ git annex version
    git-annex version: 6.20160613-g1e4e6f4

    ~$ git annex calckey /some/file/some/wh.ere
    git-annex: Not in a git repository.
    CallStack (from HasCallStack):
      error, called at ./Git/CurrentRepo.hs:55:37 in main:Git.CurrentRepo
