The hat became motionless once more; applause broke out, though it was punctured, for the first time in Harry's memory, with muttering and whispers. All across the Great Hall students were exchanging remarks with their neighbors, and Harry, clapping along with everyone else, knew exactly what they were talking about.
"Branched out a bit this year, hasn't it?" said Ron, his eyebrows raised.
"Too right it has," said Harry.
The Sorting Hat usually confined itself to describing the different qualities looked for by each of the four Hogwarts houses and its own role in Sorting them. ...
Harry Potter and the Order of the Phoenix
I don't quite understand "Too right it has" both semantically and grammatically. Is it an idiom? I guess it means: the hat is too right. But it should be written as: "too right it is" instead. How should we understand it here?