Service extensions should invoke a refresh method upon refresh

[Jan-Wijbrand Kolman]

Currently the service_extensions will invoke an uninstall followed by an install
to refresh an extension. This may lead to data loss if the extension's uninstall
properly removes all extension's traces - e.g. services.

We can solve this is if the install.py of an extension is supposed to have a
refresh method that is called from the extensions service instead.

I put it under Silva-1.1 too, but its probably too late to inlcude it there.

[Martijn Faassen (faassen)]

Removing this from Silva-1.1, as it's indeed too late. You're right though. I
have a half-finished extension manager system sitting in CVS that has more
thinking about this, but that's probably too much work to introduce in 1.2 as
well... Then of course there's the migration I hope to start doing using Zope 3
utilities..

[Martijn Faassen (faassen)]

Not planning this in for Silva-1.2

[Andy Altepeter (aaltepet)]

the Silva trunk (2.2) now supports real extension refreshes, not simply uninstall/install.

[Kit Blake (kitblake)]

We need to solve a related problem with refreshes, namely that metadata sets get flushed and any adjustments (like changing role guards) don't persist.

[Kit Blake (kitblake)]

But I'll 'Fix release' this issue.