Emacs footnote 自动排序

2.10 Footnotes 的教程里提到了：

C-c C-x f
The footnote action command.
When the cursor is on a footnote reference, jump to the definition. When it is at a definition, jump to the (first) reference.

Otherwise, create a new footnote. Depending on the option org-footnote-define-inline18, the definition will be placed right into the text as part of the reference, or separately into the location determined by the option org-footnote-section.

When this command is called with a prefix argument, a menu of additional options is offered:
s Sort the footnote definitions by reference sequence. During editing,
…

但是一直没搞明白那个 prefix argument 是什么键，所以一直是随便摁的，今天看到 reddit 的帖子，里面提到是 C-u。

Footnote 是跳转到文尾，还有一个 Internal link，可以跳转到文内设定的地方。

方法是 <<id>> ，然后使用 [id] 或 [[id][description]] 设置连接跳转到 id 处。