[Evolution-hackers] Upgrade path fix

[Ettore Perazzoli <ettore ximian com>]

Hello,

right now components upgrade from an existing Evolution version when
they are first activated.  However, that's bad since they get all
activated at the same time and it's not clear to the shell when that
happens (so e.g. if there are progress dialogs they'll interfere and
stuff).

So I have added a upgradeFromVersion() method in Evolution-Component.idl
that you are now supposed to implement for your component to upgrade the
configuration settings.  If you don't implement that method, the shell
won't complain -- but you should.

So we should move all the migration stuff into this method.

Please let me know if this method is not enough for your component's
needs so we can massage it more in that case.

The mechanism is similar to that of the old e-config-upgrade, i.e. it
stores the version number in a GConf key and attempts an upgrade if the
current version number is higher than the old one.

BTW, I am not sure if we are going to be able to support upgrading from
versions older than 1.4 easily...  Maybe we can still invoke
e-config-upgrade and make it convert to 1.4 format, then run the
upgradeFromVersion()?

Thoughts?

-- Ettore