upgrade-charm and default configuration values

[Mark Shuttleworth]

On 08/03/16 19:19, Michael Nelson wrote:
> I think the updating of default config options is a good discussion to
> have, but more specifically, the question I feel needs answering is:
> Can a charm not only update the default config options (to point to a
> new major version, for eg.) but also update it's support to only
> handle that new default option. This is, afaiui, what seems to happen.
> More details below... 

I think the answer has to be that the charm author can make the changes
needed to move to a better offering.

We might want to provide mechanisms to warn the user, for example by
refusing to update the charm unless the user either provides updated
config or accepts the new default, so that this doesn't happen silently.
But the fact is that the whole idea of charming is to use shared
operational knowledge, not just of how to stand up the software but how
to run it over time, and that MUST include the ability to evolve.

Mark