$ git clone -n https://src.fedoraproject.org/rpms/plasma-desktop.git /var/lib/mock/f42-build-side-1-3578399-46814/root/chroot_tmpdir/scmroot/plasma-desktop
Cloning into '/var/lib/mock/f42-build-side-1-3578399-46814/root/chroot_tmpdir/scmroot/plasma-desktop'...
$ git fetch origin 067947679f938f99573e5086b5c4142b0def487a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-desktop
 * [new ref]         067947679f938f99573e5086b5c4142b0def487a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0679476 6.4.1