$ git clone -n https://src.fedoraproject.org/rpms/rpm-ostree.git /var/lib/mock/f41-build-side-1-2768943-32100/root/chroot_tmpdir/scmroot/rpm-ostree
Cloning into '/var/lib/mock/f41-build-side-1-2768943-32100/root/chroot_tmpdir/scmroot/rpm-ostree'...
$ git fetch origin 81f1748122f86c319af3141c6bc9f94563a85b6c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rpm-ostree
 * [new ref]         81f1748122f86c319af3141c6bc9f94563a85b6c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 81f1748 Add libzstd-devel BuildRequires