$ git clone -n https://src.fedoraproject.org/rpms/libsigc++.git /var/lib/mock/f45-build-16969-494/root/chroot_tmpdir/scmroot/libsigc++
Cloning into '/var/lib/mock/f45-build-16969-494/root/chroot_tmpdir/scmroot/libsigc++'...
$ git fetch origin 30b34c2a3bfe2ad2076f45b9e950e1e4f0fe7e2e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libsigc++
 * [new ref]         30b34c2a3bfe2ad2076f45b9e950e1e4f0fe7e2e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 30b34c2 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild