$ git clone -n https://src.fedoraproject.org/rpms/vex.git /var/lib/mock/f40-build-2251921-54162/root/chroot_tmpdir/scmroot/vex
Cloning into '/var/lib/mock/f40-build-2251921-54162/root/chroot_tmpdir/scmroot/vex'...
$ git fetch origin 96e94647f76b9961d9b17e3fdad04f68cf09fa88:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/vex
 * [new ref]         96e94647f76b9961d9b17e3fdad04f68cf09fa88 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 96e9464 Convert to %autorelease and %autochangelog