The return value from strbuf_branchname() is confusing and
useless: it's 0 if the whole name was consumed by an @-mark,
but otherwise is the length of the original name we fed.
No callers actually look at the return value, so let's just
get rid of it.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>