$ git clone -n https://src.fedoraproject.org/rpms/dtk6core.git /var/lib/mock/f42-build-868435-176111/root/chroot_tmpdir/scmroot/dtk6core
Cloning into '/var/lib/mock/f42-build-868435-176111/root/chroot_tmpdir/scmroot/dtk6core'...
$ git fetch origin b514f76476de49d4c58f5633b4e58ff268bb340d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/dtk6core
 * [new ref]         b514f76476de49d4c58f5633b4e58ff268bb340d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b514f76 6.0.25