Ref T7643. When you do something like this:
- Edit a task description.
- Click "Show Details" on the resulting transaction.
- Get a prose diff dialog showing the change.
...now add some "Old" and "New" tabs. These are useful for:
- reverting to the old text by copy/pasting;
- reading just the new/old text if the diff is noisy;
- sometimes just nice to have?
(This looks a little rough but I didn't want to put a negative margin on tab groups inside dialogs? Not sure what the best fix here is.)
