Reviewing all the upgrade code by hand is really slow and prone to errors. More if we need to check that from time to time.

Try to create one parser, able to split those db/upgrade.php files into proper upgrade blocks and then:

• check versions order.
• check each block has one call to corresponding upgrade_xxx_savepoint() method
• check that versions in "if" sentence and versions in savepoint call match.
• check other situations, missing upgrade code, missing if blocks, more than 1 savepoint in one block...