Fix Shell lexer

lib/linguist/extensions.yml

@@ -410,6 +410,7 @@ Self:
   - .self
 Shell:
   :lexer: bash
+  :default_lexer: true
   :ext:
   - .sh
   - .zsh

lib/linguist/language.rb

@@ -11,10 +11,12 @@ module Linguist
 
       @name_index[language.name.downcase] = language
 
-      if language.default_lexer? || !@lexer_index.key?(language.lexer)
+      if attributes[:default_lexer] || language.default_lexer?
         @lexer_index[language.lexer.downcase] = language
       end
 
+      @lexer_index[language.lexer.downcase] ||= language
+
       language.extensions.each do |extension|
         @extension_index[extension] = language
         @extension_index[extension.sub(/^./, '')] = language
@@ -87,6 +89,7 @@ module Linguist
     Language.create(
       :name => name,
       :lexer => options[:lexer],
+      :default_lexer => options[:default_lexer],
       :extensions => options[:ext],
       :popular => popular.include?(name)
     )

test/test_language.rb

@@ -19,12 +19,16 @@ class TestLanguage < Test::Unit::TestCase
   end
 
   def test_find_by_lexer
+    assert_equal Language['C'], Language.find_by_lexer('c')
+    assert_equal Language['C++'], Language.find_by_lexer('cpp')
+    assert_equal Language['Java'], Language.find_by_lexer('java')
+    assert_equal Language['JavaScript'], Language.find_by_lexer('javascript')
+    assert_equal Language['OCaml'], Language.find_by_lexer('ocaml')
     assert_equal Language['Perl'], Language.find_by_lexer('perl')
     assert_equal Language['Python'], Language.find_by_lexer('python')
     assert_equal Language['Ruby'], Language.find_by_lexer('ruby')
-    assert_equal Language['C++'], Language.find_by_lexer('cpp')
-    assert_equal Language['JavaScript'], Language.find_by_lexer('javascript')
     assert_equal Language['Scheme'], Language.find_by_lexer('scheme')
+    assert_equal Language['Shell'], Language.find_by_lexer('bash')
     assert_equal Language['Text'], Language.find_by_lexer('kt')
   end