add_update

Add an entry to the BatchOperation, to be updated on the server when the operation is run.

The update will return the updated version of entry. entry is reffed by the function, so may be freed after it returns.

Note that a single batch operation should not operate on a given Entry more than once, as there's no guarantee about the order in which the batch operation's operations will be performed.

callback will be called as specified in the documentation for add_query, with an operation_type of UPDATE.

Parameters:

this	a BatchOperation
entry	the Entry to update
callback	a BatchOperationCallback to call when the update is finished, or null
user_data	data to pass to the callback function

Returns:

operation ID for the added update, or 0