Make the update check an opt-in option
Description of the feature
Recent version of GIMP have gained the ability to check for updates by accessing https://www.gimp.org/gimp_versions.json and showing the About dialog with a suitable notification message, prompting the user to visit https://www.gimp.org/downloads/ and downloading a new version or an updated Windows installer or DMG file.
This is a useful feature, and can also be disabled by either the user or by packagers, but it is still a unexpected new event and certainly has some potential to surprise users. As an uncommanded event (i.e. something happens without an user action) it can also raise some suspicions (we've had some reports about this already).
Instead of the About dialog with the update message, I propose to do the following:
- show a (new) dialog that only addresses the fact that GIMP can now check for updates
- offer the following actions there:
- check for an update once, right then and there
- set up to check automatically once a week (the current default behavior)
- postpone this dialog and remind the user later (next start or when the next check would happen)
- disable automatic update checking
Some of those options can be merged into a checkbox that is effectively an equivalent of the current update check option in preferences. We could probably also show the preferences dialog with the update section pre-elected instead of an entirely new dialog, if feasible.