$ git clone -n https://src.fedoraproject.org/rpms/system-rules.git /var/lib/mock/f38-build-side-42-init-devel-593275-26150/root/chroot_tmpdir/scmroot/system-rules
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-593275-26150/root/chroot_tmpdir/scmroot/system-rules'...
$ git fetch origin 2858c2af62cf7aaf580fc529d6f89ef5f5cf0a18:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/system-rules
 * [new ref]         2858c2af62cf7aaf580fc529d6f89ef5f5cf0a18 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2858c2a Rebuilt for https://fedoraproject.org/wiki/Fedora_38_Mass_Rebuild