$ git clone -n https://src.fedoraproject.org/rpms/R-pbdZMQ.git /var/lib/mock/f38-build-723889-99307/root/chroot_tmpdir/scmroot/R-pbdZMQ
Cloning into '/var/lib/mock/f38-build-723889-99307/root/chroot_tmpdir/scmroot/R-pbdZMQ'...
$ git fetch origin c4d94819a3308ad97fc505766ef53b4cdf84ab03:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-pbdZMQ
 * [new ref]         c4d94819a3308ad97fc505766ef53b4cdf84ab03 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c4d9481 R-maint-sig mass rebuild