'git check-ref-format' checks for the presence of at least one '/', the
idea being that there should be no refs directly below 'refs/', so there
should be a category like 'heads/' or 'tags/' in a refname.
Try and make this clearer in the man page.
Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>