feat(editor): replace undo-tree with undo-fu and vundo

Also replace undohist with undo-fu-session.

Overall this seems to yield a more reliable undo history, as undo-fu and
vundo supposedly operate with vanilla emacs undo history state, while
undo-tree supposedly does some custom tweaks to the undo state.

core/siren-core-modules.el

@@ -39,9 +39,10 @@
 (require 'siren-rainbow)
 (require 'siren-recentf)
 (require 'siren-savehist)
-(require 'siren-undo-tree)
-(require 'siren-undohist)
+(require 'siren-undo-fu)
+(require 'siren-undo-fu-session)
 (require 'siren-uniquify)
+(require 'siren-vundo)
 (require 'siren-which-key)
 (require 'siren-whitespace)
 

modules/editor/siren-undo-fu-session.el

@@ -0,0 +1,23 @@
+;;; siren-undo-fu-session.el --- jimeh's Emacs Siren: undo-fu-session configuration.
+
+;;; Commentary:
+
+;; Basic configuration for undo-fu-session.
+
+;;; Code:
+
+(use-package undo-fu-session
+  :demand
+  :custom
+  (undo-fu-session-directory (siren-cache-dir "undo-fu-session"))
+  (undo-fu-session-linear nil)
+  (undo-fu-session-compression 'gz)
+  (undo-fu-session-file-limit nil)
+  (undo-fu-session-incompatible-files '("/COMMIT_EDITMSG\\'"
+                                        "/git-rebase-todo\\'"))
+
+  :config
+  (global-undo-fu-session-mode))
+
+(provide 'siren-undo-fu-session)
+;;; siren-undo-fu-session.el ends here

modules/editor/siren-undo-fu.el

@@ -0,0 +1,22 @@
+;;; siren-undo-fu.el --- jimeh's Emacs Siren: undo-fu configuration.
+
+;;; Commentary:
+
+;; Basic configuration for undo-fu.
+
+;;; Code:
+
+(use-package undo-fu
+  :demand
+  :general
+  ("M--" 'undo-fu-only-undo)
+  ("M-_" 'undo-fu-only-redo)
+  ("s-z" 'undo-fu-only-undo)
+  ("s-Z" 'undo-fu-only-redo)
+
+  :custom
+  (undo-fu-allow-undo-in-region nil)
+  (undo-fu-ignore-keyboard-quit t))
+
+(provide 'siren-undo-fu)
+;;; siren-undo-fu.el ends here

modules/editor/siren-vundo.el

@@ -0,0 +1,18 @@
+;;; siren-vundo.el --- jimeh's Emacs Siren: vundo configuration.
+
+;;; Commentary:
+
+;; Basic configuration for vundo.
+
+;;; Code:
+
+(use-package vundo
+  :demand
+  :general
+  ("C-x u" 'vundo)
+
+  :custom
+  (vundo-glyph-alist vundo-unicode-symbols))
+
+(provide 'siren-vundo)
+;;; siren-vundo.el ends here