Then when that image gets updated the selector 20200916 updates and the browser requests a new image with the new url.
UPDATE: In response to a question: We don't want to clear the cache. We prefer to bust the cache. This way when an asset is updated, the modified date increases and the clients can use that to request a new asset. Then we can set the browser cache time to be unlimited but the new resource will be requested anyway when it is updated. That way, if we update the page, but the font doesn't change, the browser will continue to cache. the font.
We'd like to do the same thing for a custom font (yes we have a custom font that we update), but the same selector trick doesn't work.
/content/dam/static/fonts/icon-font/icon-font.1234.ttf and /content/dam/static/fonts/icon-font/icon-font.ttf.transform/original/icon-font.20200916.ttf both return a 404.