bug#69078: [PATCH] esh-mode: Allow eshell-kill-output to actually kill the output.

[Tomas Volf <~@wolfsden.cz>]

Before this commit, the function eshell-kill-output, despite the name,
did not allow to kill the output, it always just deleted it.  This
commit fixes that, allowing to do the kill with C-u.

This mimics how comint mode operates, so from this commit C-c C-o and
C-u C-c C-o will work the same way in eshell-mode and shell-mode.

* lisp/eshell/esh-mode.el (eshell-kill-output): New optional argument,
kill.
---
The function name is misleading (and in comint is is called
coming-delete-output), but changing it could break code, so I do not think it is
worth it.  Adding the argument should be enough.

I do not have a copyright assignment, however the change is trivial, and mostly
copied from comint-delete-output, so I do not think it is necessary.

 lisp/eshell/esh-mode.el | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/lisp/eshell/esh-mode.el b/lisp/eshell/esh-mode.el
index fd279f61673..882fc67b9a1 100644
--- a/lisp/eshell/esh-mode.el
+++ b/lisp/eshell/esh-mode.el
@@ -832,13 +832,18 @@ This function should be in the list `eshell-output-filter-functions'."
       eshell-last-output-start
     eshell-last-output-end))

-(defun eshell-kill-output ()
-  "Kill all output from interpreter since last input.
-Does not delete the prompt."
-  (interactive)
+(defun eshell-kill-output (&optional kill)
+  "Delete all output from interpreter since last input.
+If KILL (interactively, the prefix), save the killed text in the
+kill ring.
+
+This command does not delete the prompt."
+  (interactive "P")
   (save-excursion
     (goto-char (eshell-beginning-of-output))
     (insert "*** output flushed ***\n")
+    (when kill
+      (copy-region-as-kill (point) (eshell-end-of-output)))
     (delete-region (point) (eshell-end-of-output))))

 (defun eshell-show-output (&optional arg)
--
2.41.0