This should resolve all problem on developer machines when switching branches or when restoring previous Moodle databases. It also prevents any potential problems during upgrades such as concurrent DB modification and resolves chicken egg problems in future caching upgrades.
Discussed with David, both points were valid but finally
we agreed about to consider the "no upgrade needed" exit
a normal/succesful one, mainly because it keeps previous
behavior the same (exit non-zero only for real errors).
As Eloy Lafuente noticed in the tracker discussion, we display the
information about the current version in the browser window title but
not at the screen itself. The patch fixes that by displaying the
information in the page heading instead of the page title.
Eloy's original idea to put the information into the grey message box
would require a change of [upgradesure,core_admin] string because
unfortunately it does not expect $a as an object but as a plain string.
The commit introduces four new constants that can be used to declare a
maturity level of Moodle core and, in the future, of extension plugins.
If the administrator is about to install or upgrade Moodle to a version
that is not considered as production-ready yet, a warning is displayed
before any change in the database.
Petr Škoda