$ git clone -n https://src.fedoraproject.org/rpms/plasma-welcome.git /var/lib/mock/f42-build-side-1-3578425-46814/root/chroot_tmpdir/scmroot/plasma-welcome
Cloning into '/var/lib/mock/f42-build-side-1-3578425-46814/root/chroot_tmpdir/scmroot/plasma-welcome'...
$ git fetch origin 7e90573b63925c7c2cf32e8c21b88a4a57a4d6b9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-welcome
 * [new ref]         7e90573b63925c7c2cf32e8c21b88a4a57a4d6b9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7e90573 6.4.1