jail -c -m pkgbase using a different branch requires -U

[bdrewery]

~/git/poudriere21 # poudriere jail -c -j 16amd64 -v 16 -m pkgbase
[00:00:00] Creating 16amd64 fs at /poudriere/jails/16amd64... done
[00:00:01] Installing 16 amd64 from pkg+https://pkg.freebsd.org/ ...pkg: Setting ABI requires setting OSVERSION, guessing the OSVERSION as: 1600000
Updating pkgbase repository catalogue...
pkg: https://pkgmir.geo.freebsd.org/FreeBSD:16:amd64/base_release_0/meta.txz: Not Found
pkg: https://pkgmir.geo.freebsd.org/FreeBSD:16:amd64/base_release_0/data.pkg: Not Found
pkg: https://pkgmir.geo.freebsd.org/FreeBSD:16:amd64/base_release_0/data.tzst: Not Found
pkg: https://pkgmir.geo.freebsd.org/FreeBSD:16:amd64/base_release_0/packagesite.pkg: Not Found
pkg: https://pkgmir.geo.freebsd.org/FreeBSD:16:amd64/base_release_0/packagesite.tzst: Not Found
Unable to update repository pkgbase
Error updating repositories!

~/git/poudriere21 # poudriere jail -c -j 16amd64 -v 16 -m pkgbase=base_weekly
[00:00:00] Error: [63491] /usr/local/share/poudriere/jail.sh:create_jail:116:Must specify URL to use -m pkgbase=repodir with -U
Exiting with status 1

~/git/poudriere21 # poudriere jail -c -j 16amd64 -v 16 -m pkgbase=base_weekly -U https://pkg.freebsd.org/
[00:00:00] Creating 16amd64 fs at /poudriere/jails/16amd64... done
[00:00:01] Installing 16 amd64 from https://pkg.freebsd.org/ ...pkg: Setting ABI requires setting OSVERSION, guessing the OSVERSION as: 1600000
Updating pkgbase repository catalogue...
Fetching meta.conf: 100%     179 B   0.2 kB/s    00:01
Fetching data: 100%    83 KiB  85.3 kB/s    00:01
Processing entries: 100%
pkgbase repository update completed. 528 packages processed.
All repositories are up to date.
pkg: Setting ABI requires setting OSVERSION, guessing the OSVERSION as: 1600000
Updating pkgbase repository catalogue...
...

We shouldn't require -U https://pkg.freebsd.org/ for using not base_release_0 branch.