$ git clone -n https://src.fedoraproject.org/rpms/mock.git /var/lib/mock/f40-build-2613517-64071/root/chroot_tmpdir/scmroot/mock
Cloning into '/var/lib/mock/f40-build-2613517-64071/root/chroot_tmpdir/scmroot/mock'...
$ git fetch origin e6bfba6ef17158d782c24056b0855f5c20271aba:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mock
 * [new ref]         e6bfba6ef17158d782c24056b0855f5c20271aba -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e6bfba6 Update mock to 5.5-1