Images polute ipynb diff

User reports (&8015 (comment 939559711)):

Hey Eduardo, hope you're doing well. I'm very excited to see Notebook diffs become a real thing! I always commit my notebooks with output (because I wouldn't wanna have to re-run the notebook to see what the results were) and output often contains plots (images). These plots make the notebook diffs very clunky because of the amount of scrolling involved. Maybe you've got an idea to solve this?

My idea for what it's worth: cut image output short e.g. instead of displaying the bytes that make up the image display "" vs. ""

Jupyter Notebooks embed large images as base64, which become part of the diff. That is great if we want to display the image as diffable, but we are not at that point yet and the base64 diffs just add unnecessary noise.