Commit 14111fc (git: submodule honor -c credential.* from
command line, 2016-02-29) accidentally wrote $HTTP_URL. It
happened to work because we ended up with "credential..helper",
which we treat the same as "credential.helper", applying it
to all URLs.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>