$ git clone -n https://github.com/xcp-ng-rpms/kernel.git /var/lib/mock/v8.3-u-ysionneau1-9436-28179/root/chroot_tmpdir/scmroot/kernel
Cloning into '/var/lib/mock/v8.3-u-ysionneau1-9436-28179/root/chroot_tmpdir/scmroot/kernel'...
$ git fetch origin 31ba3bb134043a380e1c15ae6213fb32c459fce9:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/kernel
 * [new ref]             31ba3bb134043a380e1c15ae6213fb32c459fce9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 31ba3bb13 bump release for test build