$ git clone -n https://src.fedoraproject.org/rpms/mosquitto.git /var/lib/mock/f42-build-3384254-45084/root/chroot_tmpdir/scmroot/mosquitto
Cloning into '/var/lib/mock/f42-build-3384254-45084/root/chroot_tmpdir/scmroot/mosquitto'...
$ git fetch origin b75b25423401d6ef8449a05123d7ad524f289ebb:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mosquitto
 * [new ref]         b75b25423401d6ef8449a05123d7ad524f289ebb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b75b254 Update to 2.0.21