Git diff view better focus on diffs

[Otterpocket]

Clicking on a single changed file in the Git panel focuses on the file in the buffer diff, but it still allows you to see all the changes on other files. I believe this makes it easy to get lost in other diffs by overscrolling.

I think it would be more intuitive if we showed the diff of only the one file and then had a button like “x Changes” that showed the multi-buffer diff.