FIX: when moving posts, retain creator and date from OP

app/models/post_mover.rb

@@ -22,11 +22,15 @@ class PostMover
   def to_new_topic(title, category_id=nil)
     @move_type = PostMover.move_types[:new_topic]
 
+    post = Post.find_by(id: post_ids.first)
+    raise Discourse::InvalidParameters unless post
+
     Topic.transaction do
       move_posts_to Topic.create!(
-        user: user,
+        user: post.user,
         title: title,
-        category_id: category_id
+        category_id: category_id,
+        created_at: post.created_at
       )
     end
   end

db/migrate/20151107041044_fix_incorrect_topic_creator_after_move.rb

@@ -0,0 +1,12 @@
+class FixIncorrectTopicCreatorAfterMove < ActiveRecord::Migration
+  def up
+    execute "UPDATE topics SET user_id = p.user_id
+             FROM posts p
+             WHERE p.topic_id = topics.id AND
+              p.post_number = 1 AND
+              p.user_id <> topics.user_id"
+  end
+
+  def down
+  end
+end

spec/models/post_mover_spec.rb

@@ -64,7 +64,7 @@ describe PostMover do
           expect(TopicUser.find_by(user_id: user.id, topic_id: topic.id).last_read_post_number).to eq(p3.post_number)
 
           expect(new_topic).to be_present
-          expect(new_topic.featured_user1_id).to eq(another_user.id)
+          expect(new_topic.featured_user1_id).to eq(p4.user_id)
           expect(new_topic.like_count).to eq(1)
 
           expect(new_topic.category).to eq(category)
@@ -112,7 +112,7 @@ describe PostMover do
           moved_to.reload
           expect(moved_to.posts_count).to eq(3)
           expect(moved_to.highest_post_number).to eq(3)
-          expect(moved_to.featured_user1_id).to eq(another_user.id)
+          expect(moved_to.user_id).to eq(p1.user_id)
           expect(moved_to.like_count).to eq(1)
           expect(moved_to.category_id).to eq(SiteSetting.uncategorized_category_id)