Updater warning to prevent skipping major versions

[PVince81]

Upgrading directly from OC 5 to OC 7 is not supported.

To avoid this situation to produce unpredictable result, the update process should have an additional check to make sure that major versions are not skipped.
Whenever it detects that this is the case, it will refuse to update.

@karlitschek refuse or warn ?

CC @MTRichards @craigpg

[PVince81]

Just to be clear, this is for the update process in core, the one that shows you the page where you click "Upgrade now".

Care needs to be taken as well that the check also blocks CLI updates.

[karlitschek]

Refuse. Because it will otherwise trigger bugs as we have seen in the bug tracker

[MTRichards]

Completely agree. We know several instances where this is a problem. But, it should tell the admin to upgrade to the next major version first when it refuses to upgrade.

[LukasReschke]

I think we also needs to add this to the updater app then.

@VicDeo pointed out that this requires changes on the server-side. Can you please elaborate again? Thanks.

[karlitschek]

@LukasReschke The idea is that the update server only send 7 if 6 is the current version. But this only handles the updater case but not the rpm or tar upgrade.

[LukasReschke]

Sure. Just wanted to ensure that this gets fixed as well :-)

[ghost]

@LukasReschke
Ref for the updater/appstore part: owncloud/appstore-issues#4

[VicDeo]

Added a version comparison to refuse downgrade/skipping major releases with Updater owncloud/updater#35

[LukasReschke]

I played around with that: #11163