Merge branch 'ps/more-sign-compare'

More -Wsign-compare fixes. * ps/more-sign-compare: sign-compare: avoid comparing ptrdiff with an int/unsigned commit-reach: use `size_t` to track indices when computing merge bases shallow: fix -Wsign-compare warnings builtin/log: fix remaining -Wsign-compare warnings builtin/log: use `size_t` to track indices commit-reach: use `size_t` to track indices in `get_reachable_subset()` commit-reach: use `size_t` to track indices in `remove_redundant()` commit-reach: fix type of `min_commit_date` commit-reach: fix index used to loop through unsigned integer prio-queue: fix type of `insertion_ctr`