$ git clone -n https://src.fedoraproject.org/rpms/trunk.git /var/lib/mock/f40-build-1209524-22540/root/chroot_tmpdir/scmroot/trunk
Cloning into '/var/lib/mock/f40-build-1209524-22540/root/chroot_tmpdir/scmroot/trunk'...
$ git fetch origin 6feca60fce38e47dbee5ce0958f88b8635dc0b20:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/trunk
 * [new ref]         6feca60fce38e47dbee5ce0958f88b8635dc0b20 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6feca60 upgrade to trunk 0.20.1