wp-admin/includes/class-wp-upgrader-skin.php:225Performs an action before an update.
public function before() {}Introduced in 2.8.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/class-wp-upgrader-skin.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.