GitLab

	* eshell/em-unix.el (eshell/diff): Before calling the `diff'
	function, ensure that the third argument is turned into a NIL if
	the string is otherwise completely empty (either no characters, or
	all tabs/spaces).  This fixes a bug from a user who found himself
	unable to customize `diff-switches' and still use Eshell's diff
	command.