changegroup: store source and url in the `hookargs` dict We store the source and url of the current data into `transaction.hookargs` this let us inherit it from upper layers that may have created a much wider transaction. We have to modify bundle2 at the same time to register the source and url in the transaction. We have to do it in the same patch otherwise, the `addchangegroup` call would fill these values and the hook calling will crash because of the duplicated 'source' and 'url' arguments passed to the hook call.