Re: [PATCH 05/20] check_object(): convert to new revindex API

> Replace direct accesses to the revindex with calls to
> 'offset_to_pack_pos()' and 'pack_pos_to_index()'.
> 
> Since this caller already had some error checking (it can jump to the
> 'give_up' label if it encounters an error), we can easily check whether
> or not the provided offset points to an object in the given pack. This
> error checking existed prior to this patch, too, since the caller checks
> whether the return value from 'find_pack_revindex()' was NULL or not.