Charli xcx has released her new single and video, “Rock Music,” and at two minutes, its brevity stands in stark contrast to the outsize amount of discussion it will spark about her new direction in the post-“Brat” era. Most crucially, fans now have a chance to decide whether she was being closer to the truth when she was indicating it would be rock music or when she was laughingly suggesting it wouldn’t be rock at all. The answer to all these questions seems to be: yes. And whatever it is or isn’t, her followers are coming together in unison in saying they are ready for a lot more than a minute and 55 seconds of it. Among the immediate comments on the YouTube link for the track: “The concept of a song titled rock music that isn’t rock music but it’s still rock music.…