allow default options for Tilt filters

[Kallin]

I'm working on a Rails app, using the Haml Gem w/ :markdown filter along with RedCarpet. We're having trouble finding a clean way to set options on the Tilt template. When rendering the tiltbase filter in haml, https://github.com/haml/haml/blob/main/lib/haml/filters/tilt_base.rb , the code looks like

      def self.render(name, source, indent_width: 0)
        text = ::Tilt["t.#{name}"].new { source }.render
        return text if indent_width == 0
        if text.frozen?
          text.gsub(/^/, ' ' * indent_width)
        else
          text.gsub!(/^/, ' ' * indent_width)
        end
      end

It would be nice if there were a way to set options, as the initialize method in the Tilt libraries template method, which is what is being instantiated here, does accept an options hash https://github.com/rtomayko/tilt/blob/master/lib/tilt/template.rb#L60 . In our case, it's a redcarpet template we're using, https://github.com/rtomayko/tilt/blob/b6338e5e6d2be7d57f5d6fdfcb8b1161fe222fb3/lib/tilt/redcarpet.rb .

As a workaround, we're doing this in a rails initializer:

module MyCompany
  class MarkdownTemplate < Tilt::RedcarpetTemplate
    def initialize(file = nil, line = 1, options = {}, &block)
      options[:autolink] = true
      options[:hard_wrap] = true
      super
    end
  end
end

Tilt.register(MyCompany::MarkdownTemplate, 'markdown')

This works, but would much prefer to have an option where we could tell Haml to use a set of default options for a given filter. I guess we could also implement our own haml filter, but seems like overkill. A simple way to set default options per haml filter would be nice.

Would love to hear the team's thoughts, and I'm happy to work on a PR if you think this is appropriate.