$ git clone -n https://src.fedoraproject.org/rpms/topgit.git /var/lib/mock/f45-build-37284-712/root/chroot_tmpdir/scmroot/topgit
Cloning into '/var/lib/mock/f45-build-37284-712/root/chroot_tmpdir/scmroot/topgit'...
$ git fetch origin 4a5c391e47e51270006a82a4729a1effa7f2b874:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/topgit
 * [new ref]         4a5c391e47e51270006a82a4729a1effa7f2b874 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4a5c391 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild