zig-format-on-save: File digest doesn't match, so undo history will be discarded

[Inc0n]

Sometimes, the following would happen on save and result in losses of undo-history.

It is determined that zig-format-on-save is the culprit, and setting it to nil can be a workaround.

buffer-undo-list is not empty. Do you want to recover now? (y or n) y File digest doesn’t match, so undo history will be discarded.