Add CommonMarker support

Gemfile

@@ -37,6 +37,7 @@ group :secondary do
   gem 'asciidoctor', '>= 0.1.0'
   gem 'liquid'
   gem 'maruku'
+  gem 'commonmarker'
 
   if RUBY_VERSION > '1.9.3'
     gem 'prawn', '>= 2.0.0'

lib/tilt/commonmarker.rb

@@ -0,0 +1,21 @@
+require 'tilt/template'
+require 'commonmarker'
+
+module Tilt
+  class CommonMarkerTemplate < Template
+    self.default_mime_type = 'text/html'
+
+    def prepare
+      @engine = nil
+      @output = nil
+    end
+
+    def evaluate(scope, locals, &block)
+      CommonMarker.render_html(data, :default)
+    end
+
+    def allows_script?
+      false
+    end
+  end
+end

test/tilt_commonmarkertemplate_test.rb

@@ -0,0 +1,20 @@
+require 'test_helper'
+require 'tilt'
+
+begin
+  require 'tilt/commonmarker'
+
+  class CommonMarkerTemplateTest < Minitest::Test
+    test "preparing and evaluating templates on #render" do
+      template = Tilt::CommonMarkerTemplate.new { |t| "# Hello World!" }
+      assert_equal "<h1>Hello World!</h1>\n", template.render
+    end
+
+    test "can be rendered more than once" do
+      template = Tilt::CommonMarkerTemplate.new { |t| "# Hello World!" }
+      3.times { assert_equal "<h1>Hello World!</h1>\n", template.render }
+    end
+  end
+rescue LoadError => boom
+  warn "Tilt::CommonMarkerTemplate (disabled)"
+end