In my CRUD app I would like to add a duplicate feature, in which an existing object’s data is used to prepopulate the form. The naive way I started with was:

def duplicate(conn, %{"id" => item_id}) do
  item = Repo.get!(Item, item_id)
  changeset = Ecto.Changeset.change(item)

  render(conn, "new.html", changeset: changeset)
end

where new.html renders a form with form_for pointing to the POST method.

BUT this does not work, as phoenix_ecto overrides the POST method in the form by setting the hidden _method field to put, because it’s noticed that the changeset refers to an existing item in the database, as shown here: https://github.com/phoenixframework/phoenix_ecto/blob/master/lib/phoenix_ecto/html.ex#L315

What is the idiomatic way of duplicating a Changeset that refers to an actual record, so that a new entry is created, without having to manually remove the __meta__ field from the changeset?