$ git clone -n https://src.fedoraproject.org/rpms/gentoo.git /var/lib/mock/f45-build-9751-408/root/chroot_tmpdir/scmroot/gentoo
Cloning into '/var/lib/mock/f45-build-9751-408/root/chroot_tmpdir/scmroot/gentoo'...
$ git fetch origin 1b36bcace4c2f4ce70d7dda16d2ac1a16db7f9a4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gentoo
 * [new ref]         1b36bcace4c2f4ce70d7dda16d2ac1a16db7f9a4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1b36bca Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild