File: wp-admin/includes/class-theme-upgrader.php

Turns on maintenance mode before attempting to upgrade the active theme.

Turns off maintenance mode after upgrading the active theme.

Deletes the old theme during an upgrade.

Gets the WP_Theme object for a theme.

Upgrades several themes at once.

Checks that the package source contains a valid theme.

Initializes the upgrade strings.

Initializes the installation strings.

Checks if a child theme is being installed and its parent also needs to be installed.

Don’t display the activate and preview actions to the user.

Install a theme package.

Upgrades a theme.