The proper way to update Tumbleweed

Thanks for this article, I have a Laptop where I use Tumbleweed as I like to not have the exact same version on all machines (makes me too incompatible with everything else) and like rolling release Distros.

And until today I always updated with `zypper ref && zypper up` as `zypper dup` told me it wants to do stuff which surely wasn't holy anymore.
I always thought a miss-configured repo or something similar caused this, and as it seemed to work with `zypper up` and it is a not often used machine anyway I did not bother to look something up (not even looked in the man page, I must admit).

So thanks for lifting this riddle for me! :)