Save backup files under Emacs’ cache directory

configuration.org

@@ -97,6 +97,19 @@ I set it up early so I can use it in ~use-package~ calls immediately.
                 mult)))))
 #+END_SRC
 
+*** Make a backup filename under ~user-emacs-cache-directory~
+
+Taken from [[http://ergoemacs.org/emacs/emacs_set_backup_into_a_directory.html][Xah’s site]].
+
+#+BEGIN_SRC emacs-lisp
+(defun xah/backup-file-name (fpath)
+    "Return a new file path for FPATH under `user-emacs-cache-directory'"
+    (let* ((backup-root-dir (concat user-emacs-cache-directory "/backup"))
+           (file-path (replace-regexp-in-string "[A-Za-z]:" ""))
+           (backup-file-path (replace-regexp-in-string "//" "/" (concat backup-root-dir file-path "~"))))
+      (make-directory (file-name-directory backup-file-path) (file-name-directory backup-file-path))
+      backup-file-path))
+#+END_SRC
 ** Check if we are running under Termux
 
 We need to do things differently, if so.
@@ -1047,10 +1060,7 @@ Because I’m a sysadmin, too.
 (use-package files
   :ensure nil
   :config
-  (setq backup-directory-alist
-        `((".*" . ,temporary-file-directory)))
-  (setq auto-save-file-name-transforms
-        `((".*" ,temporary-file-directory t))))
+  (setq make-backup-file-name-function 'xah/backup-file-name))
 #+END_SRC
 
 ** ~whitespace~