This is a nice-to-have feature deferred from #666: - Progress to show which database migration is currently being run (in the web browser and/or on the command line)
Proposal: - refactor core/Updater.php and plugins/CoreUpdater/Controller.php, moving Piwik_Updater::update() to the Controller; this would eliminate the messiness of a callback
Doing it in the UI would be cool, but not a must have. Doing it in CLI sounds more useful as most big users would use CLI for upgrades (if this is explained in the upgrade screen UI as an inline help)
I'm tempted to mark as wontfix...
Instead of visual feedback, we could make sure all queries run separately, then, we could update DB state between each query, to ensure smooth upgrade even if it breaks in the middle (but low priority)