format-patch: pick up branch description when no ref is specified We only try to get branch name in "format-patch origin" case or similar and not "format-patch -22" where HEAD is automatically added. Without correct branch name, branch description cannot be added. Make sure we always get branch name. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>