It just stayed with me from ViM. Maybe it should even be M-~ :)
@@ -542,4 +542,6 @@ Version 2016-02-16"
(add-hook 'eshell-mode-hook
(lambda () (local-set-key (kbd "C-d") #'eshell-C-d)))
(global-set-key (kbd "C-x ~") 'toggle-char-case)
(require 'magithub)
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