bug#51226: 29.0.50; `align' doc string is unclear

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Fri, 15 Oct 2021 12:04:01 +0200
> 
> 
> `align' doesn't mention the prefix arg in the doc string, but in certain
> modes, different alignment rules are picked based on what prefix you
> give to the command.  For instance, text mode:
> 
>     ;; With a numeric prefix argument, or C-u, space delimited text
>     ;; tables will be aligned.
>     (text-column
>      (regexp   . "\\(^\\|\\S-\\)\\([ \t]+\\)\\(\\S-\\|$\\)")
>      (group    . 2)
>      (modes    . align-text-modes)
>      (repeat   . t)
>      (run-if   . ,(lambda ()
>                     (and current-prefix-arg
>                          (not (eq '- current-prefix-arg))))))
> 
>     ;; With a negative prefix argument, lists of dollar figures will
>     ;; be aligned.
>     (text-dollar-figure
>      (regexp   . "\\$?\\(\\s-+[0-9]+\\)\\.")
>      (modes    . align-text-modes)
>      (justify  . t)
>      (run-if   . ,(lambda ()
>                     (eq '- current-prefix-arg))))
> 
> It's also not clear why `M-x align' in text modes do nothing -- you
> have to give it a prefix to make it do anything.

John, could you help us out here by explaining this stuff?