Improve undoing of RET in comint and eshell

* lisp/comint.el (comint-send-input):
(comint-accumulate):
* lisp/eshell/esh-mode.el (eshell-send-input): Before sending input to
the process, delete it and reinsert it again.  Undoing this
insertion with 'C-/' will delete the region, moving the process mark
back to its original position (bug#49484).

1 files changed, 8 insertions, 0 deletions

diff --git a/lisp/eshell/esh-mode.el b/lisp/eshell/esh-mode.el
index 2b5a4647e06..a054cd66e27 100644
--- a/lisp/eshell/esh-mode.el
+++ b/lisp/eshell/esh-mode.el
@@ -616,6 +616,14 @@ newline."
                   (and eshell-send-direct-to-subprocesses
                        proc-running-p))
         (insert-before-markers-and-inherit ?\n))
+      ;; Delete and reinsert input.  This seems like a no-op, except
+      ;; for the resulting entries in the undo list: undoing this
+      ;; insertion will delete the region, moving the process mark
+      ;; back to its original position.
+      (let ((text (buffer-substring eshell-last-output-end (point)))
+            (inhibit-read-only t))
+        (delete-region eshell-last-output-end (point))
+        (insert text))
       (if proc-running-p
           (progn
             (eshell-update-markers eshell-last-output-end)