Comment 12 for bug 338002

When someone makes a comment on a diff, they're clearly talking about that particular diff. So, if the "latest" diff on the review page gets updated, old comments could be automatically annotated to say that they were reactions to an older version of the diff (a link to which would be provided).

That way the diff displayed is always the most recent, but the history is still there and there's no confusion about which comments are about which iterations of the diff. (The fact that the historical diffs are slightly less convenient to reach is okay, because in practice it's very rare to need to see them anyway. It's enough to know that a comment is about an older diff; one doesn't actually have to *see* the older diff.)