$ git clone -n https://src.fedoraproject.org/rpms/greyhounds.git /var/lib/mock/f45-build-13044-446/root/chroot_tmpdir/scmroot/greyhounds
Cloning into '/var/lib/mock/f45-build-13044-446/root/chroot_tmpdir/scmroot/greyhounds'...
$ git fetch origin b987778c8a98c2e73c9007e364fd745459bb8624:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/greyhounds
 * [new ref]         b987778c8a98c2e73c9007e364fd745459bb8624 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b987778 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild