serve: use repository pointer to get config

serve: use repository pointer to get config

A few of the v2 "serve" callbacks ignore their repository parameter and
read config using the_repository (either directly or implicitly by
calling wrapper functions). This isn't a bug since the server code only
handles a single main repository anyway (and indeed, if you look at the
callers, these repository parameters will always be the_repository). But
in the long run we want to get rid of the_repository, so let's take a
tiny step in that direction.

As a bonus, this silences some -Wunused-parameter warnings.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>