Add option to run on markdown filetype

[alerque]

Currently we're assuming people :set ft=commonmark to use this, but given the rest of the ecosystem it's more likely they will want to use markdown or even another filetype, but use this as the syntax. We need a way to enable this use case.

[fmoralesc]

In vim-pandoc/vim-pandoc-syntax#333 I created a flavor of the pandoc syntax that defers to this when g:pandoc#syntax#flavor is `"ancillary", and extends the supported syntax for more pandoc-aware block types.

[alerque]

Good, that's probably a good path forward until I figure out how to compile commonmark-hs and it gets all the extensions we need, which probably won't be until Pandoc itself switches internally for PFM.

[fmoralesc]

👍 For now the issue will be in making the lua method performant. In my limited testing it made editing slow to a crawl.

[alerque]

At the moment this is setup strictly as a syntax highlighter, it doesn't require the filetype being set to match. My current use case is keeping my usual selection of ft=markdown or ft=pandoc and then running :set syntax=commonmark when I want to run this.

I'm not quite sure how to codify this workflow or another appropriate one for others.

[fmoralesc]

Have you used my ancillary syntax flavor in vim-pandoc-syntax? It makes using this transparent for the pandoc filetype, I've been using it like this for the past few days.

[alerque]

No, I haven't. I did see it, but I was mucking around with using commonmark-hs in my vim-pandoc-syntax repo and haven't gotten around to cleaning it so I can go back to a sane working condition and switch branches.

My only question is .... vim-pandoc-syntax is easy since we can set it up to load this however we like, but how does this play with people who want to use it stand-alone (and may even have other plugins watching the markdown file type)?

[fmoralesc]

Setting up an autocommand should work, although it won't be as clean as having it integrated with the filetype plugin. In case people are using some other markdown plugin, they should probably also ask upstream to add support. That is not our problem. I don't mean to say that we shouldn't make it easy (for example, we could optionally generate some generic autocommands to latch on specific filetypes, a bit like modules are implemented in vim-pandoc), but I don't see it as a big concern overall.