Reid Barton [off-list ref] writes:
When the working directory is not the top of the working tree, git-
add--interactive fails silently and confusingly.
Sheesh, you got me worried.
This is a non issue; git-add--interactive is not for direct end user
consumption. It relies on being run from git-add wrapper, which does
cdup to the top of the work tree before launching add--interactive
helper.