On http://www.reviewboard.org/docs/manual/dev/users/tools/post-review/#posting-committed-code, it claims that you can use a single revision id for --revision-range. However, it didn’t work when I tried it, so I made it work.

The strategy is, when given a single revision as the argument of --revision-range, find the first parent of that revision, and use that as the first revision of the diff (and the given revision as the second revision).