Perhaps it makes more sense to display the working copy commit just
above the changes in the working copy commit, even though that means
that the order between the working copy commit and the parent becomes
the opposite of the order in `jj log`.
I'm preparing to publish an early version before someone takes the
name(s) on crates.io. "jj" has been taken by a seemingly useless
project, but "jujube" and "jujube-lib" are still available, so let's
use those.