$ git clone -n https://src.fedoraproject.org/rpms/mock-centos-sig-configs.git /var/lib/mock/f45-build-19011-539/root/chroot_tmpdir/scmroot/mock-centos-sig-configs
Cloning into '/var/lib/mock/f45-build-19011-539/root/chroot_tmpdir/scmroot/mock-centos-sig-configs'...
$ git fetch origin fba2f65a1dafc21019a28a1a72e22bfc57220280:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mock-centos-sig-configs
 * [new ref]         fba2f65a1dafc21019a28a1a72e22bfc57220280 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fba2f65 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild