Comment # 7 on bug 1154973 from Fabian Vogt

(In reply to Jonathan Kang from comment #6)
> It's mainly about when to set and reset upgradeMode.
> 
> Running "pkcon update" leads to calling get-updates and update-packages. A
> list
> of update candidates will be passed from get-updates to update-packages.
> 
> * If upgradeMode is set in get-updates and reset to FALSE when it's done,
> update-packages won't be able to perform a dup-like action in Tumbleweed.
> * If upgradeMode is set in get-updates and not reset when finished, removing/
> installing packages will lead to a full dup-style system upgrade in
> Tumbleweed.
> * We can try to set upgradeMode in update-packages, but update-packages is
> responsible for updating specific packages and upgrading the whole system.

I see two options:

a) A hack: Let get-updates a fake "this-is-a-dup" package as marker which is
passed to update-packages later.
b) Just not support update-packages on its own on TW. Picking out just a few
packages from a new snapshot is not guaranteed to work anyway.