$ git clone -n https://src.fedoraproject.org/rpms/R-pbdZMQ.git /var/lib/mock/f42-build-side-1-3501310-45974/root/chroot_tmpdir/scmroot/R-pbdZMQ
Cloning into '/var/lib/mock/f42-build-side-1-3501310-45974/root/chroot_tmpdir/scmroot/R-pbdZMQ'...
$ git fetch origin 58491e7730018fca19092a1e6514e42e2d0b71ec:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-pbdZMQ
 * [new ref]         58491e7730018fca19092a1e6514e42e2d0b71ec -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 58491e7 R-maint-sig mass rebuild