$ git clone -n https://src.fedoraproject.org/rpms/erlang-cowboy.git /var/lib/mock/f41-build-side-1-2811254-32927/root/chroot_tmpdir/scmroot/erlang-cowboy
Cloning into '/var/lib/mock/f41-build-side-1-2811254-32927/root/chroot_tmpdir/scmroot/erlang-cowboy'...
$ git fetch origin 9f5a028ba2cc5c676f12b0e61fcda4259a1db963:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/erlang-cowboy
 * [new ref]         9f5a028ba2cc5c676f12b0e61fcda4259a1db963 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9f5a028 Cosmetic changes