Make Language.[] and Language.find_by(alias|name) ignore case

This makes it easier to find a Linguist::Language for a fenced code
block in Markdown, where language names are often specified in
lowercase.

lib/linguist/language.rb

@@ -62,7 +62,7 @@ module Linguist
       end
 
       # Language name index
-      @index[language.name] = @name_index[language.name] = language
+      @index[language.name.downcase] = @name_index[language.name.downcase] = language
 
       language.aliases.each do |name|
         # All Language aliases should be unique. Raise if there is a duplicate.
@@ -70,7 +70,7 @@ module Linguist
           raise ArgumentError, "Duplicate alias: #{name}"
         end
 
-        @index[name] = @alias_index[name] = language
+        @index[name.downcase] = @alias_index[name.downcase] = language
       end
 
       language.extensions.each do |extension|
@@ -164,7 +164,7 @@ module Linguist
     #
     # Returns the Language or nil if none was found.
     def self.find_by_name(name)
-      @name_index[name]
+      @name_index[name.downcase]
     end
 
     # Public: Look up Language by one of its aliases.
@@ -178,7 +178,7 @@ module Linguist
     #
     # Returns the Lexer or nil if none was found.
     def self.find_by_alias(name)
-      @alias_index[name]
+      @alias_index[name.downcase]
     end
 
     # Public: Look up Languages by filename.
@@ -227,7 +227,7 @@ module Linguist
     #
     # Returns the Language or nil if none was found.
     def self.[](name)
-      @index[name]
+      @index[name.downcase]
     end
 
     # Public: A List of popular languages

test/test_language.rb

@@ -303,6 +303,21 @@ class TestLanguage < Test::Unit::TestCase
     assert_nil Language['defunkt']
   end
 
+  def test_find_ignores_case
+    assert_equal 'AGS Script', Language['ags script'].name
+    assert_equal 'AGS Script', Language['ags sCRIPT'].name
+  end
+
+  def test_find_by_name_ignores_case
+    assert_equal 'AGS Script', Language.find_by_name('ags script').name
+    assert_equal 'AGS Script', Language.find_by_name('ags sCRIPT').name
+  end
+
+  def test_find_by_alias_ignores_case
+    refute_includes Language['AGS Script'].aliases, 'AGS'
+    assert_equal 'AGS Script', Language.find_by_alias('AGS').name
+  end
+
   def test_name
     assert_equal 'Perl',   Language['Perl'].name
     assert_equal 'Python', Language['Python'].name