bug#31796: 27.1; dired-do-find-regexp-and-replace fails to find multiline regexps

[Juri Linkov]

>> Another backup plan is to use ripgrep.  Its multiline handling with -U
>> also allows to search words ignoring any whitespace, even newlines.
>> This is like isearch-lax-whitespace using search-whitespace-regexp
>> when it contains a newline, e.g. "[ \t\r\n]+".
>
> Right. It has a problem of its own, though: it still outputs a file name
> per line, even when a match is spread across several lines (unlike
> pcregrep). So we're left guessing where a given multiline match ends.
>
> Also, 'sort' doesn't seem to be able to treat both : and \0 as separators
> at the same time.
>
> Here's a rough patch, for illustration.

Thanks, now finally it's possible to search text ignoring whitespace
between words, for example:

  Find regexp: file[    
]+names

finds everything correctly, even though current implementation maybe
not the most elegant.

> It's kind of working, but I'm not loving it.

What do you think about using the option `rg --json`?
Emacs has the fast JSON parsing library now, so using
JSON output would be more reliable.