$ git clone -n https://src.fedoraproject.org/rpms/nginx.git /var/lib/mock/f41-build-815869-149783/root/chroot_tmpdir/scmroot/nginx
Cloning into '/var/lib/mock/f41-build-815869-149783/root/chroot_tmpdir/scmroot/nginx'...
$ git fetch origin 4e49378a2e81c4f670b6c0091ac898d6fb443cd4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/nginx
 * [new ref]         4e49378a2e81c4f670b6c0091ac898d6fb443cd4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4e49378 Perl 5.40 rebuild