Comment 5 for bug 2048870

Not sure I see the need for two separate commands for initializing an offer and extending it. How about:

`juju add-offer foo:x` -> if foo has no offers yet, create an offer on endpoint x. If foo already has offers, append 'x' to the list of offered endpoints

Also I'd rather have `juju offer` be called `juju set-offer`, to hint at the fact that you're expected to provide an exclusive list of endpoints to be activated, and the command will deactivate all that are not mentioned in the list.

We have a similar convention in ops, where `add/remove-port` offers the delta semantics, and `set-port` gives you the replace semantics.