autocomplete: match static metatags case-sensitively.

Fix rating:S not matching rating:s.

app/logical/autocomplete_service.rb

@@ -161,7 +161,7 @@ class AutocompleteService
 
   def autocomplete_static_metatag(metatag, value)
     values = STATIC_METATAGS[metatag.to_sym]
-    results = values.select { |v| v.starts_with?(value) }.sort.take(limit)
+    results = values.select { |v| v.starts_with?(value.downcase) }.sort.take(limit)
 
     results.map do |v|
       { label: metatag + ":" + v, value: v }

test/unit/autocomplete_service_test.rb

@@ -201,6 +201,12 @@ class AutocompleteServiceTest < ActiveSupport::TestCase
         assert_autocomplete_equals(["order:score", "order:score_asc"], "order:sco", :tag_query)
       end
 
+      should "match static metatags case-insensitively" do
+        assert_autocomplete_equals(["rating:safe"], "rating:S", :tag_query)
+        assert_autocomplete_equals(["rating:questionable"], "rating:Q", :tag_query)
+        assert_autocomplete_equals(["rating:explicit"], "rating:E", :tag_query)
+      end
+
       should "ignore bogus tags" do
         assert_autocomplete_equals([], "x"*200, :tag_query)
         assert_autocomplete_equals([], "http://www.google.com", :tag_query)