Default CommonMarker options?

[dometto]

It turns out commonmarker by default removes HTML tags from markdown for safety. Since we already implement our own sanitization, this seems superfluous: indeed, other renders such as kramdown already leave HTML elements in by default.

So it may be deisrable to override the commonmarker defaults and activate its :UNSAFE option. However, this would require overriding yet another block of code from github-markup, like here, which would be a bit messy.

Alternatively, we could make use of the fact that github-markup allows passing in an options hash with commonmarker settings, e.g.: GitHub::Markup.render("test.md", "hello <bad> world", options: {commonmarker_opts: [:UNSAFE]})

However, since this option does not exist for kramdown yet, it would mean we would have to manage our defaults for commonmark and kramdown in two different ways: overriding the Proc for the latter, and passing an options hash in our call to GitHub::Markup.render for the former. I've therefore opened a PR at github-markup: https://github.com/github/markup/pull/1543

If this is merged, it woud allow us to refactor the way we override options for the markdown rendering gems.