$ git clone -n https://src.fedoraproject.org/rpms/R-rlang.git /var/lib/mock/f42-build-3530691-46321/root/chroot_tmpdir/scmroot/R-rlang
Cloning into '/var/lib/mock/f42-build-3530691-46321/root/chroot_tmpdir/scmroot/R-rlang'...
$ git fetch origin f7f538f877dd4e7a0b17b852f0f157db48e3a54f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-rlang
 * [new ref]         f7f538f877dd4e7a0b17b852f0f157db48e3a54f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f7f538f Update to latest version