bug#46515: Repeat mode

[Juri Linkov]

>> repeat.el doesn't describe the key binding, but it does say a repeat
>> mode is active. Kmacro is so smart that it aranges for the repeat key to
>> be based on whatever key the command was invoked with.
>
> Unlike `indent-rigidly', `kmacro' message
>
>   (Type e to repeat macro)
>
> is displayed on every keypress, so it's a good example.
> Now added in the following patch applied over the previous patch.

Here is another incremental patch that adds more messaging:

diff --git a/lisp/repeat.el b/lisp/repeat.el
index 3c8be63c84..a322afed1d 100644
--- a/lisp/repeat.el
+++ b/lisp/repeat.el
@@ -349,7 +349,16 @@ repeat-mode
   :global t :group 'convenience
   (if (not repeat-mode)
       (remove-hook 'post-command-hook 'repeat-post-hook)
-    (add-hook 'post-command-hook 'repeat-post-hook)))
+    (add-hook 'post-command-hook 'repeat-post-hook)
+    (let* ((keymaps nil)
+           (commands (all-completions
+                      "" obarray (lambda (s)
+                                   (and (commandp s)
+                                        (get s 'repeat-map)
+                                        (push (get s 'repeat-map) keymaps))))))
+      (message "Repeat mode is enabled for %d commands and %d keymaps"
+               (length commands)
+               (length (delete-dups keymaps))))))
 
 (defun repeat-post-hook ()
   "Function run after commands to set transient keymap."
@@ -362,7 +371,10 @@ repeat-post-hook
         (let ((map (copy-keymap repeat-map)))
           (let (keys)
             (map-keymap (lambda (key _) (push (key-description (vector key)) 
keys)) map)
-            (message "To repeat type %s" (mapconcat #'identity keys ", ")))
+            (message "To repeat type %s%s"
+                     (mapconcat #'identity keys ", ")
+                     (when repeat-exit-key
+                       (format ", or %s to exit" (key-description 
repeat-exit-key)))))
           (when repeat-exit-key
             (define-key map repeat-exit-key 'ignore))
           (set-transient-map map))))))