$ git clone -n https://src.fedoraproject.org/rpms/gmp-ecm.git /var/lib/mock/f45-build-11331-429/root/chroot_tmpdir/scmroot/gmp-ecm
Cloning into '/var/lib/mock/f45-build-11331-429/root/chroot_tmpdir/scmroot/gmp-ecm'...
$ git fetch origin c312ef65a8f882088ab4f526e0fd9abd0f892f73:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gmp-ecm
 * [new ref]         c312ef65a8f882088ab4f526e0fd9abd0f892f73 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c312ef6 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild