artists: simplify artist url saving code.

Refactor the way artist urls are saved so that artist url validations
run before the artist is saved, not after.

test/unit/artist_test.rb

@@ -168,11 +168,16 @@ class ArtistTest < ActiveSupport::TestCase
       assert_equal(["minko"], Artist.find_all_by_url("http://minko.com/x/test.jpg").map(&:name))
     end
 
-    should "not allow duplicates" do
+    should "not find duplicates" do
       FactoryGirl.create(:artist, :name => "warhol", :url_string => "http://warhol.com/x/a/image.jpg\nhttp://warhol.com/x/b/image.jpg")
       assert_equal(["warhol"], Artist.find_all_by_url("http://warhol.com/x/test.jpg").map(&:name))
     end
 
+    should "not include duplicate urls" do
+      artist = FactoryGirl.create(:artist, :url_string => "http://foo.com http://foo.com")
+      assert_equal(["http://foo.com"], artist.url_array)
+    end
+
     should "hide deleted artists" do
       FactoryGirl.create(:artist, :name => "warhol", :url_string => "http://warhol.com/a/image.jpg", :is_active => false)
       assert_equal([], Artist.find_all_by_url("http://warhol.com/a/image.jpg").map(&:name))
@@ -407,5 +412,18 @@ class ArtistTest < ActiveSupport::TestCase
       tag.reload
       assert_equal(Tag.categories.artist, tag.category)
     end
+
+    context "when updated" do
+      setup do
+        @artist = FactoryGirl.create(:artist)
+        @artist.stubs(:merge_version?).returns(false)
+      end
+
+      should "create a new version" do
+        assert_difference("@artist.versions.count") do
+          @artist.update(:url_string => "http://foo.com")
+        end
+      end
+    end
   end
 end