It's unfortunate that git-annex sorta defeats git's rename detection.
When an annexed file is moved to a different directory (specifically, a directory that is shallower or deeper than the old directory), the symlink often has to change. And so git log cannot --follow back through the rename history, since all it has to go on is that symlink, which it effectively sees as a one line file containing the symlink target.
One way to fix this might be to do the
git annex fix after the rename
is committed. This would mean that a commit would result in new staged
changes for another commit, which is perhaps startling behavior.
The other way to fix it is to stop using symlinks, see smudge.