$ git clone -n https://src.fedoraproject.org/rpms/plasma-welcome.git /var/lib/mock/f41-build-824414-154063/root/chroot_tmpdir/scmroot/plasma-welcome
Cloning into '/var/lib/mock/f41-build-824414-154063/root/chroot_tmpdir/scmroot/plasma-welcome'...
$ git fetch origin 1b406fee6857a594492c8ee76df06563b21205a5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-welcome
 * [new ref]         1b406fee6857a594492c8ee76df06563b21205a5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1b406fe rebuild