$ git clone -n https://src.fedoraproject.org/rpms/gitit.git /var/lib/mock/f40-build-2720063-73031/root/chroot_tmpdir/scmroot/gitit
Cloning into '/var/lib/mock/f40-build-2720063-73031/root/chroot_tmpdir/scmroot/gitit'...
$ git fetch origin 890f2ae11e0169be969f165e4a0c040717f6e1f2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gitit
 * [new ref]         890f2ae11e0169be969f165e4a0c040717f6e1f2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 890f2ae rebuild