Should offer ability to detect generic vi: ft=* style language designations

[Donald Guy]

Hi 👋 if anyone else actually see's this note to self.

I have recently started using bat as my goto ~pager. In working with some stuff I've already found myself in want of sharkdp/bat#1600 but I suspect that it should go into syntect proper rather than be grafted on in bat

I am looking to get into more rust, so I am setting this aside in this fork as a "good first issue" type of dealio

Cause I want the experience at least as much as I want the feature shipped immediately

For what its worth, I plan to crib from https://github.com/ctlajoie/vscode-modelines/blob/master/src/modelines.ts for the generic detection logic

if someone wants to beat me to it :-)

[Donald Guy]

It looks like there isn't any need to change outside the one function. It is already always called when extension is indeterminete

https://github.com/trishume/syntect/blob/2d8e3061c9cd746ce50b6548037911b96939b6bd/src/parsing/syntax_set.rs#L253-L258

so its just a question of having (optional?) fallback to a default pattern if the syntax doesn't specify one (or if it does but none match?)

This is to say we need to stick our (varying result) checker at the bottom of the first_line_cache

https://github.com/trishume/syntect/blob/2d8e3061c9cd746ce50b6548037911b96939b6bd/src/parsing/syntax_set.rs#L696-L715

except that it obviously then can't only be a static regex to index match as it is now

    #[derive(Debug)]
struct FirstLineCache {
    /// (first line regex, syntax index) pairs for all syntaxes with a first line regex
    regexes: Vec<(Regex, usize)>,
}

needing to resolve to a dynamic result (which should itself cross-check for a definition?)

there is ... probably a relevant trait for this - but I am a rust noob

If we were okay with naivety we could use a capture group against mode/ft I think