$ git clone -n https://src.fedoraproject.org/rpms/filesystem.git /var/lib/mock/f45-build-43637-804/root/chroot_tmpdir/scmroot/filesystem
Cloning into '/var/lib/mock/f45-build-43637-804/root/chroot_tmpdir/scmroot/filesystem'...
$ git fetch origin 68948b3ba9c90b30d13c0434f054be04cff64878:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/filesystem
 * [new ref]         68948b3ba9c90b30d13c0434f054be04cff64878 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 68948b3 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild