[PATCH v2 11/13] list-objects: clarify how promised blobs are excluded

When "--exclude-promisor-objects" is passed by the user, commands like git-rev-list(1) will exclude any objects part of a promisor pack. For blobs this logic is handled in `process_blob()` with the following logic:

    if (ctx->revs->exclude_promisor_objects &&
        !repo_has_object_file(the_repository, &obj->oid) &&
        is_promisor_object(ctx->revs->repo, &obj->oid))
            return;

It is somewhat puzzling that we use `repo_has_object_file()` to check for existence of the blob because this function will cause us to fetch missing objects in case they are part of a promisor pack. As such, one may wonder whether the logic to exclude promised blobs is completely broken.

As it turns out it's not broken: when "--exclude-promisor-objects" is set we also unset the global `fetch_if_missing` variable, which causes `do_oid_object_info_extended()` to not fetch any promised objects at all.

Clarify this logic by using `has_object()`, which doesn't fetch promised objects by default.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 list-objects.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)