feat(emacs): Configure Ediff

- Restore window configuration on quit.
- Very simple, half-broken helper for resolving Syncthing conflicts.
  - Doesn't automatically delete the conflict file after resolve. }:\

users/crumb/programs/emacs/modules/syd-ediff.el

@@ -0,0 +1,19 @@
+;;; syd-ediff.el -*- lexical-binding: t; -*-
+
+(require 'syd-prelude)
+
+(with-eval-after-load 'ediff
+  (setq ediff-diff-options "-w" ; Ignore whitespace
+        ediff-window-setup-function #'ediff-setup-windows-plain)
+  (defvar syd--ediff-saved-wconf nil)
+
+  ;; Restore window config after quitting Ediff.
+  (syd-add-hook 'ediff-before-setup-hook
+    (defun syd--ediff-save-wconf-h ()
+      (setq syd--ediff-saved-wconf (current-window-configuration))))
+  (syd-add-hook '(ediff-quit-hook ediff-suspend-hook)
+    (defun syd--ediff-restore-wconf-h ()
+      (when (window-configuration-p syd--ediff-saved-wconf)
+        (set-window-configuration syd--ediff-saved-wconf)))))
+
+(provide 'syd-ediff)