builtin/gc: fix signedness issues in ODB-related functionality
There are a couple of signedness issues in ODB-related functionality. These are not a problem because we disable -Wsign-compare in this file, but once we move these functions into "odb/source-files.c" they will result in warnings. Fix those issues: - In `too_many_loose_objects()` we receive a signed limit, but compare it with the unsigned actual number of loose objects. This is fixed by bailing out immediately when the limit is smaller than or equal to zero, which we also do similarly in other places. The warning is then squelched via a cast. - In `find_base_packs()` we compare the signed size of the pack against the unsigned limit. As the pack size is always going to be a positive file size it's safe to cast it to an unsigned value. - In `odb_optimize()` we compare the unsigned `keep_pack.nr` value against the signed `gc_auto_pack_limit`. We only reach this code when `too_many_packs()` returns true-ish, and that can only happen when `gc_auto_pack_limit > 0`. Consequently, we can fix the warning by casting the limit to an unsigned value. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>