wp-admin/includes/upgrade.php:1683Execute changes made in WordPress 2.9.
function upgrade_290() { global $wp_current_db_version; if ( $wp_current_db_version < 11958 ) { /* * Previously, setting depth to 1 would redundantly disable threading, * but now 2 is the minimum depth to avoid confusion. */ if ( 1 === (int) get_option( 'thread_comments_depth' ) ) { update_option( 'thread_comments_depth', 2 ); update_option( 'thread_comments', 0 ); } }}Introduced in 2.9.0. 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.