* lisp/image/image-dired-util.el (image-dired-thumb-name): Always end thumbnail name in ".jpg" and simplify naming to just use the SHA-1 hash. (Bug#57961) * test/lisp/image/image-dired-util-tests.el (image-dired-thumb-name/image-dired): Adjust test for the above change. * etc/NEWS: Announce the above change.