Add doom/switch-theme; a more sensible load-theme

load-theme doesn't disable previously enabled themes before switching.
doom/switch-theme does.

This remaps any keys bound to load-theme to doom/switch-theme.

core/autoload/ui.el

@@ -103,3 +103,20 @@ presentations."
       (mapc #'disable-theme custom-enabled-themes))
     (doom|init-theme)
     (doom|init-fonts)))
+
+;;;###autoload
+(defun doom/switch-theme (theme)
+  "Like `load-theme', but will unload currently loaded themes before switching
+to a new one."
+  (interactive
+   (list (completing-read
+          "Load theme: "
+          (mapcar #'symbol-name
+                  (custom-available-themes)))))
+  (condition-case nil
+      (progn
+        (mapc #'disable-theme custom-enabled-themes)
+        (load-theme (intern theme) t)
+        (when (fboundp 'powerline-reset)
+          (powerline-reset)))
+    (error "Problem loading theme %s" x)))

core/core-ui.el

@@ -540,14 +540,18 @@ frame's window-system, the theme will be reloaded.")
 (setq frame-title-format '("%b – Doom Emacs"))
 ;; draw me like one of your French editors
 (tooltip-mode -1) ; relegate tooltips to echo area only
-;; prompts the user for confirmation when deleting a non-empty frame
-(define-key global-map [remap delete-frame] #'doom/delete-frame)
-
 ;; a good indicator that Emacs isn't frozen
 (add-hook 'doom-init-ui-hook #'blink-cursor-mode)
 ;; line numbers in most modes
 (add-hook! (prog-mode text-mode conf-mode) #'doom|enable-line-numbers)
 
+;; More sensibile replacements for default commands
+(define-key! 'global
+  ;; prompts the user for confirmation when deleting a non-empty frame
+  [remap delete-frame] #'doom/delete-frame
+  ;; a more sensible load-theme, that disables previous themes first
+  [remap load-theme] #'doom/switch-theme)
+
 (defun doom*fix-whitespace-mode-in-childframes (orig-fn &rest args)
   (let ((frame (apply orig-fn args)))
     (with-selected-frame frame