Add option eshell-history-append

* lisp/eshell/em-hist.el (eshell-history-append): New option.
(eshell--save-history): New function.
(eshell-hist-initialize):
(eshell-save-some-history): Replace eshell-write-history with
eshell--save-history, which respects the new option.
* doc/misc/eshell.texi (History): Document the change.
* etc/NEWS: Announce the change.  (Bug#66700)

1 files changed, 13 insertions, 3 deletions

diff --git a/lisp/eshell/em-hist.el b/lisp/eshell/em-hist.el
index cf03f8399a6..79336204847 100644
--- a/lisp/eshell/em-hist.el
+++ b/lisp/eshell/em-hist.el
@@ -116,6 +116,12 @@ If set to t, history will always be saved, silently."
                  (const :tag "Ask" ask)
                  (const :tag "Always save" t)))
 
+(defcustom eshell-history-append nil
+  "If non-nil, append new entries to the history file when saving history."
+  :type '(choice (const :tag "Overwrite history file" nil)
+                 (const :tag "Append new entries to file" t))
+  :version "30.1")
+
 (defcustom eshell-input-filter 'eshell-input-filter-default
   "Predicate for filtering additions to input history.
 Takes one argument, the input.  If non-nil, the input may be saved on
@@ -294,17 +300,21 @@ Returns nil if INPUT is prepended by blank space, otherwise non-nil."
     (if eshell-history-file-name
         (eshell-read-history nil t))
 
-    (add-hook 'eshell-exit-hook #'eshell-write-history nil t))
+    (add-hook 'eshell-exit-hook #'eshell--save-history nil t))
 
   (unless eshell-history-ring
     (setq eshell-history-ring (make-ring eshell-history-size)))
 
-  (add-hook 'eshell-exit-hook #'eshell-write-history nil t)
+  (add-hook 'eshell-exit-hook #'eshell--save-history nil t)
 
   (add-hook 'kill-emacs-query-functions #'eshell-save-some-history)
 
   (add-hook 'eshell-input-filter-functions #'eshell-add-to-history nil t))
 
+(defun eshell--save-history ()
+  "Save the history for current Eshell buffer."
+  (eshell-write-history nil eshell-history-append))
+
 (defun eshell-save-some-history ()
   "Save the history for any open Eshell buffers."
   (dolist (buf (buffer-list))
@@ -318,7 +328,7 @@ Returns nil if INPUT is prepended by blank space, otherwise non-nil."
                         (format-message
                          "Save input history for Eshell buffer `%s'? "
                          (buffer-name buf)))))
-              (eshell-write-history)))))
+              (eshell--save-history)))))
   t)
 
 (defun eshell/history (&rest args)