this change is announced here:
https://www.archlinux.org/news/base-group-replaced-by-mandatory-base-package-manual-intervention-required/

This means a couple of things:

# we need to forward the news announcement to our users, since the base metapackage was automatically pulled to our repos, and the same mitigation steps apply to our users as well.
# we need to update the installation guide since I believe the pacstrap calls need to be updated
## we need to review / update the installation media, in particular the more automated installers
# we need to review packages in the base group we repackage and determine whether their group entries can go away
# we need to review whether our helper scripts, such as the imagebuilder and vm bootstrap are impacted by this change
# we need to accomodate our openrc things towards using a metapackage as well
# we can probably drop base-meta from [pcr]
# we need to update our own infrastructure (winston / beefcake / ...) to accomodate that change, probably at least installing the base metapackage explicitly
# we need to look as base-devel and see what needs to be done there

let's go!

UPDATE:

package in base group, not in new base package (five are pulled in by the 'base' package indirectly): package:

<pre>
> cryptsetup (in 'base' dep chain)
> device-mapper (in 'base' dep chain)
> dhcpcd
> e2fsprogs (in 'base' dep chain)
> inetutils
> jfsutils
> logrotate
> lvm2
> man-db
> mdadm
> nano
> netctl
> pacman-mirrorlist (in 'base' dep chain)
> perl (in 'base' dep chain)
> reiserfsprogs
> s-nail
> sysfsutils
> texinfo
> usbutils
> vi
> xfsprogs
> your-system-sanity

for orphan in $THE_LIST_ABOVE
do grep $orphan <(pactree --sync --linear 'base')
done | sort -u

* cryptsetup <- systemd-common <- systemd <- p11-kit <-
ca-certificates-utils <- ca-certificates-mozilla <-
ca-certificates <- curl <- pacman <- base
* device-mapper <- cryptsetup <- ... ^
* e2fsprogs <- krb5 <- libtirpc <- pam <- shadow <- base
* perl <- openssl <- coreutils <- base
* pacman-mirrorlist <- pacman <- base

</pre>

packages in new base package, not in base group:
<pre>
< coreutils
< file
< filesystem
< grep
< gzip
< licenses
< sed
< tar
< xz
</pre>