The --ignore-case option was added by 3bb16a8bf2 (tag,
branch, for-each-ref: add --ignore-case for sorting and
filtering, 2016-12-04), but it was never tested. And indeed,
it does not work due to multiple bugs (which will be fixed
in subsequent patches).
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>