Eshell: Trim trailing spaces in commands

.emacs.d/lisp/init-eshell.el

@@ -70,11 +70,7 @@
 ;;; mu: no matches for search expression (4)
 ;;; See #21605 "24.3; Eshell not using stderr".
 
-;;; REVIEW: Some parsing fails
-;;; > echo -n $PATH | sed 's/:[^:]*sophos[^:]*/:/g'
-;;; :s/:]*sophos[/:]*/:/"/
-;;; Unknown modifier character ‘/’
-;;;
+;;; REVIEW: eshell/date does not support many options from GNU date.
 ;;; > date +%Z
 ;;; See #29157.
 (when (< emacs-major-version 27)
@@ -199,8 +195,6 @@
 (add-hook 'eshell-mode-hook 'ambrevar/turn-off-nobreak-char-display)
 
 ;;; History
-;;; Filter out space-beginning commands from history.
-;;; TODO: history/command hook: trim spaces.  Check `eshell-rewrite-command-hook'.
 ;;; REVIEW: history: do not save failed Eshell commands (See `eshell-last-command-status')
 ;;; Eshell commands always return 0.
 (setq eshell-input-filter
@@ -213,8 +207,17 @@
               (string= "" str)
               (string= "cd" str)
               (string-prefix-p "cd " str)
+              ;; Filter out space-beginning commands from history.
               (string-prefix-p " " str)))))
 
+(defun ambrevar/eshell-delete-trailing-whitespace (last-output-end point)
+  "Delete trailing whitespace in Eshell command.
+This is useful to avoid dumb duplicates in history."
+  (save-mark-and-excursion
+    (goto-char (point-max))
+    (delete-trailing-whitespace)))
+(add-hook 'eshell-expand-input-functions 'ambrevar/eshell-delete-trailing-whitespace)
+
 ;;; Shared history.
 (defvar ambrevar/eshell-history-global-ring nil
   "The history ring shared across Eshell sessions.")