The "rev" program is part of "util-linux-ng". Your problem may be elsewhere, because I don't believe you are missing this package. Rather, something else went wrong during the upgrade.
Perhaps the best thing to do is create a Slackware-current DVD ISO, burn that to a medium, boot from it, then instead of running "setup" you mount your local hard disk partition under "/mnt" as well as your DVD below "/var/log/mount" and then use the command
Code:
ROOT=/mnt upgradepkg /var/log/mount/slackware/*/*.t?z
to upgrade your already installed Slackware packages.
Then read the ChangeLog.txt for Slackware-current carefully, and look for packages that have been added (the word "Added" will be present in that entry, so use that in your search) and install those packages (still running from the DVD) with
Code:
ROOT=/mnt installpkg /var/log/mount/slackware/*/full_name_of_missing_package.t?z
Perhaps that will help. Also do not forget to look for *.new files which may have been left in the /etc/ directory of your harddisk (which is /mnt/etc while you are still running from the DVD) and do something wise with those.
Eric