upload-pack: use repository struct to get config

Our upload_pack_v2() function gets a repository struct, but we ignore it totally. In practice this doesn't cause any problems, as it will never differ from the_repository. But in the spirit of taking a small step towards getting rid of the_repository, let's at least starting using it to grab config. There are probably other spots that could benefit, but it's a start. Note that we don't need to pass the repo for protected_config(); the whole point there is that we are not looking at repo config, so there is no repo-specific version of the function. For the v0 version of the protocol, we're not passed a repository struct, so we'll continue to use the_repository there. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>