wp-admin/includes/upgrade.php:1968Execute changes made in WordPress 4.2.0.
function upgrade_420() {}Introduced in 4.2.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/upgrade.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.