according to archive.org that site was taken down in 2017. I doubt they have a backup of that, or that anything on that site should be kept around because it’d be horribly outdated.
that shift function would be a nice candidate for a special case of arguments to warpAffine. maybe reopen/open the issue and propose it. some newbie will surely be interested in a self-contained issue like this. I’ve just downloaded that shift.hpp function archive.org still had from the old site, just in case anyone might need it.