This is pretty trivial question sorry for this, but I searched all over the internet but didn't get the answer for this.
Why a copy is required in merge method? why it do no persist the passed entity object directly? please help me with this?

Thank you

Isn't there any explanation for this?

Consider a scenario I have a detached entity instance and if I fetch another row with same database identifier as like detached entity from database, so now I have a detached instance and a managed instance and both corresponds to the same database row. Now a if I try to merge the detached instance and instead of creating copy if the same detached instance is managed then it will leave managed instance in inconsistent state, i.e. a confusion is there about what needs to be done with the instance that is already there in Persistent context, so to avoid this merge method copies the state of detached instance and returns the managed instance.

This is fine but now this leads to a question why a transient instance is not managed directly, why a copy is needed in case of transient instance?