$ git clone -n https://src.fedoraproject.org/rpms/libvirt.git /var/lib/mock/f40-build-2676124-67851/root/chroot_tmpdir/scmroot/libvirt
Cloning into '/var/lib/mock/f40-build-2676124-67851/root/chroot_tmpdir/scmroot/libvirt'...
$ git fetch origin f4d251ad6e3ad2bfb213dc2072aa7861b061c852:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libvirt
 * [new ref]         f4d251ad6e3ad2bfb213dc2072aa7861b061c852 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f4d251a Add sources