Support on the command line plaintext and commonmark formats

Command line arguments `--to=commonmark` and
`--to=plaintext` are now supported

bin/commonmarker

@@ -55,7 +55,7 @@ def parse_options
       exit
     end
 
-    opts.on('-tFORMAT', '--to=FORMAT', String, 'Specify output format (html, xml)') do |value|
+    opts.on('-tFORMAT', '--to=FORMAT', String, 'Specify output FORMAT') do |value|
       value = value.to_sym
       options.output_format = value if format_options.include?(value)
     end
@@ -108,4 +108,8 @@ when :html
   end
 when :xml
   $stdout.write(doc.to_xml(options.active_render_options))
+when :commonmark
+  $stdout.write(doc.to_commonmark(options.active_render_options))
+when :plaintext
+  $stdout.write(doc.to_plaintext(options.active_render_options))
 end

lib/commonmarker/config.rb

@@ -25,7 +25,7 @@ module Config
         UNSAFE: (1 << 17),
         FOOTNOTES: (1 << 13)
       }.freeze,
-      format: %i[html xml].freeze
+      format: %i[html xml commonmark plaintext].freeze
     }.freeze
 
     def self.process_options(option, type)

test/test_commands.rb

@@ -29,9 +29,19 @@ def test_understands_multiple_extensions
     %w[<table> <tr> <th> a </th> <td> c </td>].each { |html| assert_includes out, html }
   end
 
-  def test_understands_format
+  def test_understands_xml_format
     out = make_bin('strong.md', '--to=xml')
     assert_includes out, '<?xml version="1.0" encoding="UTF-8"?>'
     assert_includes out, '<text xml:space="preserve">strong</text>'
   end
+
+  def test_understands_commonmark_format
+    out = make_bin('strong.md', '--to=commonmark')
+    assert_equal('I am **strong**', out)
+  end
+
+  def test_understands_plaintext_format
+    out = make_bin('strong.md', '--to=plaintext')
+    assert_equal('I am strong', out)
+  end
 end