Agree to a point,
Running the following commands should re-enable the appropriate repos…
zypper mr --enable 1 2 4
Now, the big question is whether you did your “zypper dup” with only that one repo enabled?
If you did, then you haven’t fully upgraded so indeed you should run “zypper dup” again.
Otherwise, you did your upgrade and now only want to update after a full upgrade, then you should “zypper up”
After a full upgrade (anytime thereafter regardless whether you have updated),
Can further re-enable your other repositories using the same “zypper mr” above but instead reference numbers of your other repos, and then run “zypper up” again.
Additionally,
You should know that you are upgrading/updating only to 15.0 and not 15.1 (as this Forum post is tagged)
TSU