master fb4f2aa038: * lisp/textmodes/paragraphs.el (repunctuate-sentences-filter): New function.

[jakanakaevangeli]

> +(defun repunctuate-sentences-filter (_start _end)
> +  "Search filter used by `repunctuate-sentences' to skip unneeded spaces.
> +By default, it skips occurrences that already have two spaces.
> +It is advised to put `advice-add' on this function to add more filters,
> +for example, `(looking-back (rx (or \"e.g.\" \"i.e.\") \" \") 5)'
> +with a set of predefined abbreviations to skip from adding two spaces."
> +  (not (length= (match-string 4) 2)))

Similarly to filter-buffer-substring-function, I believe it would be
better if this was a variable, on which 'add-function' could be used.
This would make it easier to set buffer locally if needed.