Add Pathname#mime_type

lib/linguist/pathname.rb

@@ -1,4 +1,5 @@
 require 'linguist/language'
+require 'mime/types'
 
 module Linguist
   class Pathname
@@ -28,6 +29,13 @@ module Linguist
       language.lexer
     end
 
+    def mime_type
+      @mime_type ||= begin
+        guesses = MIME::Types.type_for(extname)
+        guesses.first ? guesses.first.simplified : 'text/plain'
+      end
+    end
+
     def to_s
       @path.dup
     end

test/test_pathname.rb

@@ -50,4 +50,12 @@ class TestPathname < Test::Unit::TestCase
     assert_equal 'scheme', Pathname.new("itty.nu").lexer
     assert_equal 'text',   Pathname.new("defun.kt").lexer
   end
+
+  def test_mime_type
+    assert_equal 'application/ruby', Pathname.new("file.rb").mime_type
+    assert_equal 'application/javascript', Pathname.new("file.js").mime_type
+    assert_equal 'application/python', Pathname.new("itty.py").mime_type
+    assert_equal 'text/plain', Pathname.new("itty.nu").mime_type
+    assert_equal 'text/plain', Pathname.new("defun.kt").mime_type
+  end
 end