The Templates dev doc page says: "Templates can be overridden... create a sub-folder under your themes 'templates' ... copy the [mustache file] into the newly created [folder] and edit it. You should see your changes immediately if theme designer mode is on".
The core templates are not in a sub-folder, but they are in the templates folder. I created a "login.mustache" in the theme sub-folder "templates", but the changes in the template are not affecting the login page. My theme is a Boost "sub-theme".
Do I need to create the layout file ("login.php") in my theme also to enable the mustache templates?