Comment # 21 on bug 1095148 from Michal Suchanek

(In reply to Fabian Vogt from comment #20)
> (In reply to Michal Suchanek from comment #19)
> > Feel free to come up with different naming.
> > 
> > sle_release is also misleading because it obviously applies to openSUSE.
> 
> --sle-release would be perfectly fine - that --sle-release 0 means openSUSE
> is IMO obvious.

That's exactly how it is misleading. It is 0 only on Tumbleweed and that's the
reason we switch from is_opensuse to sle_release. It it was non-zero on SLE
only then it would be inverse of is_opensuse and completely meaningless.