Seems ticket #4733 is related, respectifely obsolete if this ticket is resolved.

Note that this is a "shallow" clone as it copies the object's attributes only, not its associations.

what does this mean for belongs_to associations? fk attribute gets cleared?

The foreign key attribute doesn't get cleared just the instance variable on the object which contains the associated object. An (imagined) IRB session might be:

post = Post.first
post.user_id # 1
post.instance_variable_get("@user") # nil
post.user # #<User id: 1, name: "Paul">
post.instance_variable_get("@user") # #<User id: 1, name: "Paul">

clone = post.clone
clone.user_id # 1
clone.instance_variable_get("@user") # nil
clone.user # #<User id: 1, name: "Paul">
clone.instance_variable_get("@user") # #<User id: 1, name: "Paul">

post.clear_association_cache
post.instance_variable_get("@user") # nil

Should I revert this current commit? Or a new patch is coming soon?

Sorry for the confusion. My comments were simply to explain to Kane how my patch works. Its not an indication that there is a problem with the patch. I'm happy that the patch you've committed is correct and should be left as it is.

If you're happy to, could you also commit my second patch? It removes a comment I added in #3164 which is no longer relevant.

Paul, I forgot to tell, the second patch does not apply anymore. :(

Second patch to remove incorrect comment re-based against master and attached.

FYI: the patch above was already applied. :)