Revert "Updated Query#update's field mergining logic."

This reverts commit e5df3f6.

lib/dm-core/query.rb

@@ -51,11 +51,10 @@ def update(other)
       @limit        = other.limit         unless other.limit         == nil
       @order        = other.order         unless other.order         == model.default_order
       @add_reversed = other.add_reversed? unless other.add_reversed? == false
+      @fields       = other.fields        unless other.fields        == @properties.defaults
       @links        = other.links         unless other.links         == []
       @includes     = other.includes      unless other.includes      == []
 
-      @fields == @properties.defaults ? @fields = other.fields : @fields |= other.fields
-
       update_conditions(other)
 
       self

spec/unit/query_spec.rb

@@ -219,17 +219,6 @@ class Acl
       @query.update(other).should == @query
     end
 
-    it "should merge #fields if :fields != model.properties.defaults" do
-      other = DataMapper::Query.new(@repository, Article, :fields => [ :blog_id ])
-      @query.update(other).fields.should == Article.properties.slice(:id, :author, :blog_id)
-    end
-
-    it "should replace #fields if fields == model.properties.defaults" do
-      query = DataMapper::Query.new(@repository, Article, :fields => Article.properties.defaults.map { |property| property.name })
-      other = DataMapper::Query.new(@repository, Article, :fields => [ :blog_id ])
-      query.update(other).fields.should == Article.properties.slice(:blog_id)
-    end
-
     describe 'should overwrite the attribute' do
       it '#reload? with other reload?' do
         other = DataMapper::Query.new(@repository, Article, :reload => true)
@@ -314,6 +303,11 @@ class Acl
         end
       end
 
+      it "#fields with other fields unique values" do
+        other = DataMapper::Query.new(@repository, Article, :fields => [ :blog_id ])
+        @query.update(other).fields.should == Article.properties.slice(:blog_id)
+      end
+
       it '#conditions with other conditions when they are unique' do
         # set the initial conditions
         @query.update(:title => 'On DataMapper')