Moving `substitute-command-keys' to Lisp [was: Ideas to improve the output of C-h m?]

[Drew Adams <drew.adams@oracle.com>]

Sounds good to have `substitute-command-keys'
defined in Lisp.  Thanks for working on that.
Hopefully it will have the same behavior.

FWIW, `help-fns+.el' uses a Lisp wrapper for it,
`help-substitute-command-keys' that optionally adds
(so-called) buttons for help on key descriptions
that result from `\\[...]'.

E.g. the `C-x 2' output from `\\[split-window-below]'
gets a button that links to the `describe-key' *Help*.

Perhaps that feature could be added to your Lisp
`substitute-command-keys' (in which case I'd drop my
`help-substitute-command-keys').  It'd be backward
compatible, since it just adds an optional arg - the
default behavior is vanilla `substitute-command-keys'.
___

 help-substitute-command-keys is a Lisp function in ‘help-fns+.el’.

 (help-substitute-command-keys STRING &optional ADD-HELP-BUTTONS)

 Same as `substitute-command-keys', but optionally adds buttons for help.
 Non-nil optional arg ADD-HELP-BUTTONS does that, adding buttons to key
 descriptions, which link to the key's command help.
___

The code is here:

https://www.emacswiki.org/emacs/download/help-fns%2b.el