bug#63272: 29.0.90; xref fails on long lines

[Juri Linkov <juri@linkov.net>]

>> In the real case the prefix and suffix were unique, so I didn't expect
>> that in a generated file there was a very long distance between prefix
>> and suffix.  To limit the distance between prefix and suffix I tried:
>>    C-x p g prefix.{0,100}suffix
>
> Try escaping { and }:
>
>   C-x p g prefix.\{0,100\}suffix

Thanks, this works.

> The regexp needs to use the syntax that Emacs can understand.
>
> Just the subset of it that can be translated to command like, so that Grep
> and Ripgrep can work with it too.
>
>> but xref that uses ripgrep fails to find matches.
>> So needed to fall back to ripgrep-based rgrep in this case:
>>    M-x rgrep prefix.{0,100}suffix
>> that works successfully.
>> It seems the problem is because of different regexp syntax
>> used by ripgrep and re-search-forward in xref--collect-matches-1.
>
> The conversion is performed by xref--regexp-to-extended.

Shouldn't the conversion also escape { and } ?