$ git clone -n https://src.fedoraproject.org/rpms/rust-plain.git /var/lib/mock/f45-build-43943-809/root/chroot_tmpdir/scmroot/rust-plain
Cloning into '/var/lib/mock/f45-build-43943-809/root/chroot_tmpdir/scmroot/rust-plain'...
$ git fetch origin b79ddc406789f414e0500f2fc848b48b72317872:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-plain
 * [new ref]         b79ddc406789f414e0500f2fc848b48b72317872 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b79ddc4 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild