Allow `kill-buffer' query to save the buffer first

* lisp/loadup.el ("emacs-lisp/rmc"): Preload.

* lisp/simple.el (kill-buffer--possibly-save): New function to
offer to save the buffer before killing (bug#47075).

* src/buffer.c (Fkill_buffer): Call the new function to query the
user.
(syms_of_buffer): Define symbol.

1 files changed, 7 insertions, 3 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 7adcd22d88b..509ce51b55e 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1809,10 +1809,12 @@ cleaning up all windows currently displaying the buffer to be killed. */)
     /* Query if the buffer is still modified.  */
     if (INTERACTIVE && modified)
       {
-        AUTO_STRING (format, "Buffer %s modified; kill anyway? ");
-        tem = do_yes_or_no_p (CALLN (Fformat, format, BVAR (b, name)));
-        if (NILP (tem))
+        /* Ask whether to kill the buffer, and exit if the user says
+           "no".  */
+        if (NILP (call1 (Qkill_buffer__possibly_save, buffer)))
           return unbind_to (count, Qnil);
+        /* Recheck modified.  */
+        modified = BUF_MODIFF (b) > BUF_SAVE_MODIFF (b);
       }
 
     /* Delete the autosave file, if requested. */
@@ -6474,5 +6476,7 @@ will run for `clone-indirect-buffer' calls as well.  */);
 
   DEFSYM (Qautosaved, "autosaved");
 
+  DEFSYM (Qkill_buffer__possibly_save, "kill-buffer--possibly-save");
+
   Fput (intern_c_string ("erase-buffer"), Qdisabled, Qt);
 }