feature request: undo / go back

[rattrayalex-stripe]

When making a large, mostly-straightforward codemod, clicking "enter" in rapid succession is the only tolerable modus operandi.

Sometimes, I see things that look potentially problematic, but my feeble human brain doesn't detect this until my eager pinky has already pressed "enter".

It would be nice to have a "b" (or maybe "u") shortcut to the previous diff and reevaluate.

I'm not sure how straightforward that would be to implement 😄

[rattrayalex-stripe]

(In this case, my workaround was to search-within-file for the result string, which was self-contained, in the currently visible file and its (alphabetically preceding) siblings, and I was able to find the change and verify it was ok).