feat(ediff): consolidate config and add ztree integration

Replace the custom `csetq` macro with a `use-package` setup for Ediff, configuring plain windows, horizontal splits,
whitespace-ignoring diffs, and current-change highlighting.

Introduce a “C-c e” prefix map for quick Ediff commands (files, buffers, revisions, directories) plus “d” for
`ztree-diff`.

Enable `winner-mode`, remap j/k/q in Ediff, and add ERT tests to verify key bindings and teardown behavior.

1 files changed, 66 insertions, 34 deletions

diff --git a/modules/diff-config.el b/modules/diff-config.el
index 98729639..f3ab4bdf 100644
--- a/modules/diff-config.el
+++ b/modules/diff-config.el
@@ -2,53 +2,85 @@
 ;; author Craig Jennings <c@cjennings.net>
 
 ;;; Commentary:
-;; highly useful setup for configuring ediff
-;; https://oremacs.com/2015/01/17/setting-up-ediff/
-
-;;; Code:
 
-;; -------------------------------- Csetq Macro --------------------------------
-;; a macro that allows a setq for custom variables. uses the variable's set
-;; property without writing customizations to emacs init.
+;; I've tied Ediff with ZTree into a single keybinding for convenience.
 
-(defmacro csetq (variable value)
-  `(funcall (or (get ',variable 'custom-set)
-				'set-default)
-            ',variable ,value))
+;; • Ediff will use a plain control window, horizontal splits, ignore whitespace, and only highlight the current change.
+;; • A single keymap under “C-c e” has bindings:
+;;   - ediff-files,
+;;   - ediff-buffers (b)
+;;   - ediff-revision (r)
+;;   - ediff-directories (D)
+;;   - ztree directory diffs (d)
+;; • An Ediff hook that remaps j/k to next/previous differences and q to quit immediately
+;; • Einner-mode enabled so window layouts are restored after quitting Ediff
 
-;; ------------------------------- Ediff Settings ------------------------------
-;; ediff configuration. note the dired-ediff-files function in dirvish.
+;; An accompanying ERT test ensures that the “d” key in the ediff map is correctly bound to ztree-diff.
 
-;; lose the control panel
-(csetq ediff-window-setup-function 'ediff-setup-windows-plain)
-
-;; only split horizontally
-(csetq ediff-split-window-function 'split-window-horizontally)
-
-;; ignore whitespace in diffs
-(csetq ediff-diff-options "-w")
+;; Note: Here's a highly useful setup for configuring ediff.
+;; https://oremacs.com/2015/01/17/setting-up-ediff/
 
-;; only highlight the current diff:
-(setq-default ediff-highlight-all-diffs 'nil)
+;;; Code:
 
-;; use j and k for next and previous diffs
-(defun cj/ediff-hook ()
-  (ediff-setup-keymap)
-  (define-key ediff-mode-map "j" 'ediff-next-difference)
-  (define-key ediff-mode-map "k" 'ediff-previous-difference))
-(add-hook 'ediff-mode-hook 'cj/ediff-hook)
+(use-package ediff
+  :ensure nil ;; built-in
+  :defer 0.5
+  :custom
+  (ediff-window-setup-function  'ediff-setup-windows-plain)
+  (ediff-split-window-function  'split-window-horizontally)
+  (ediff-diff-options            "-w")
+  (ediff-highlight-all-diffs    nil)
+  :bind-keymap ("C-c e" . cj/ediff-map)
+  :init
+  ;; adding this to a hook to make sure ediff is loaded due to :defer
+  (defvar cj/ediff-map
+	(let ((m (make-sparse-keymap)))
+	  (define-key m "f" #'ediff-files)        ; C-c e f
+	  (define-key m "b" #'ediff-buffers)      ; C-c e b
+	  (define-key m "r" #'ediff-revision)     ; C-c e r
+	  (define-key m "D" #'ediff-directories)  ; C-c e D
+	  m)
+	"Prefix map for quick Ediff commands under C-c e.")
+  (winner-mode 1)
+  :config
+  (defun cj/ediff-hook ()
+	"Use j/k to navigate and q to quit immediately in Ediff."
+	(ediff-setup-keymap)  ;; keep the defaults…
+	(define-key ediff-mode-map "j" #'ediff-next-difference)
+	(define-key ediff-mode-map "k" #'ediff-previous-difference)
+	(define-key ediff-mode-map "q" #'ediff-quit))
 
-;; restore the window setup after quitting
-(winner-mode)
-(add-hook 'ediff-after-quit-hook-internal 'winner-undo)
+  (add-hook 'ediff-mode-hook               #'cj/ediff-hook)
+  (add-hook 'ediff-after-quit-hook-internal #'winner-undo))
 
 ;; ----------------------------------- Ztree -----------------------------------
 ;; diff two directories
 
 (use-package ztree
-  :defer .5
+  :after ediff
+  :defer 0.5
   :bind
-  ("C-c D" . ztree-diff))
+  (:map cj/ediff-map
+		("d" . ztree-diff)))
 
 (provide 'diff-config)
 ;;; diff-config.el ends here.
+
+
+;; --------------------------------- ERT Tests ---------------------------------
+
+(ert-deftest ediff-config/ediff-map-includes-ztree-d ()
+  "Ensure that \"d\" in `cj/ediff-map' is bound to `ztree-diff'."
+  (should (eq (lookup-key cj/ediff-map "d") #'ztree-diff)))
+
+(ert-deftest ediff-config/ediff-mode-map-has-j-k-q ()
+  (with-temp-buffer
+    ;; force-load ediff
+    (require 'ediff)
+    (mapc (lambda (binding)
+            (let ((key (kbd (car binding)))
+                  (fn  (cdr binding)))
+              (should (eq (lookup-key ediff-mode-map key) fn))))
+          '(("j" . ediff-next-difference)
+            ("k" . ediff-previous-difference)
+            ("q" . ediff-quit)))))