$ git clone -n https://src.fedoraproject.org/rpms/booksorg.git /var/lib/mock/f41-build-1034385-18630/root/chroot_tmpdir/scmroot/booksorg
Cloning into '/var/lib/mock/f41-build-1034385-18630/root/chroot_tmpdir/scmroot/booksorg'...
$ git fetch origin c297d74a7ae34a324f2d8678b756725747d400a9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/booksorg
 * [new ref]         c297d74a7ae34a324f2d8678b756725747d400a9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c297d74 Fix flatpak build