Add Nix config

config.org

@@ -1229,6 +1229,18 @@
 	 (add-to-list 'auto-mode-alist '("\\.bbc\\'" . basic-mode))
    #+end_src
 
+** Nix
+   Basic editing support comes from =nix-mode=:
+
+   #+begin_src emacs-lisp
+	 (use-package nix-mode)
+   #+end_src
+
+   And =nix-update= provides a convenient way to update ~fetch~
+   blocks:
+
+   #+begin_src emacs-lisp
+	 (use-package nix-update)
    #+end_src
 
 * Tool Integrations
@@ -1527,6 +1539,14 @@
      (global-set-key (kbd "C-.") #'god-mode-all)
    #+end_src
 
+   I find it jarring and confusing to have it on and off in different
+   types of buffers, so will just disable the exemptions:
+
+   #+begin_src emacs-lisp
+     (setq god-exempt-major-modes nil)
+     (setq god-exempt-predicates nil)
+   #+end_src
+
 ** Case-flipping
    Want to be able to toggle the 'shiftedness' of a selected region,
    that is, map uppercase to lowercase and vice versa, but also map
@@ -1618,3 +1638,13 @@
    #+begin_src emacs-lisp
      (global-set-key (kbd "C-~") 'flip-region-case)
    #+end_src
+
+* Fin
+  Now that start-up is finished, [[help:gc-cons-threshold][gc-cons-threshold]] and
+  [[help:gc-cons-percentage][gc-cons-percentage]] need to be set back to reasonable values to avoid
+  memory usage getting too high.
+
+  #+begin_src emacs-lisp
+	(setq gc-cons-threshold 1000000)
+	(setq gc-cons-percentage 0.2)
+  #+end_src