Operations with themes use the wp theme command.
Theme Status
First, you can check the status, and get the accepted names, of some or all themes with:
wp theme status
Update Theme
You can update one or more themes with:
wp theme update <theme>
If you want to update all themes, use:
wp theme update --all
Delete a Theme
You can also delete a theme. It looks like it won’t delete the active theme without an extra option to force the deletion, but it might still delete a parent theme you’re using, so be careful!
If you want to delete a theme:
wp theme delete <theme>
Roll Back a Parent Theme
If you need to roll back a parent theme, you use the wp theme command with the same syntax you would for rolling back a plugin. For example, to test rolling back the theme “sometheme” to version 1.2.0:
wp theme update --version=1.2.0 --dry-run
Once you’re sure the roll-back will work, execute the command without the –dry-run option:
wp theme update --version=1.2.0