$ git clone -n https://src.fedoraproject.org/rpms/crystal-stacker-themes.git /var/lib/mock/f45-build-5746-341/root/chroot_tmpdir/scmroot/crystal-stacker-themes
Cloning into '/var/lib/mock/f45-build-5746-341/root/chroot_tmpdir/scmroot/crystal-stacker-themes'...
$ git fetch origin b1f6fe8f7a18a776aed0a8c087ee4d37d21c0507:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/crystal-stacker-themes
 * [new ref]         b1f6fe8f7a18a776aed0a8c087ee4d37d21c0507 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b1f6fe8 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild