bzr-incoming
Haha. Ok, this is actually in the bzr core as bzr missing
with some flags to tell it whether you want a bidirectional report or just
one way. They'll be improving the docs so people can find it in the future.
The source for my plugin is still available as a historical curiousity
if you're interested (it shows the full history on merges, which missing
does not).
Devel verison is accessible via bzr branch http://code.timhatch.com/bzr/bzr-incoming/