Hi,
when running git annex add in my direct mode repository, since a few days ago I only get:
$ git annex add git-annex: unknown response from git cat-file (":./Archiv/Someone missing",:./Archiv/Someone Like You Cover-fCvjvEGkTu4.flv)
The :./Archiv/Someone missing part strikes me odd because it so much looks like broken shell meta-character escaping in git-annex, but I doubt that because it stopped working just suddenly.
Still getting this myself. First I've ran into it (a few weeks ago, but I hadn't used these repos recently).
This is a bug, introduced in commit 34530e59 (release 6.20161012) and fixed in commit b530e432 (release 6.20161031).
It happens only when the filename contains a single space, so a workaround is to first add a filename without any spaces, and then rename it: