$ git clone -n https://src.fedoraproject.org/rpms/emacs-blacken.git /var/lib/mock/f40-build-2434974-60766/root/chroot_tmpdir/scmroot/emacs-blacken
Cloning into '/var/lib/mock/f40-build-2434974-60766/root/chroot_tmpdir/scmroot/emacs-blacken'...
$ git fetch origin fbcfc68111756518e749ea5764f8eebdd87f9e15:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/emacs-blacken
 * [new ref]         fbcfc68111756518e749ea5764f8eebdd87f9e15 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fbcfc68 Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild