Commits missing authors from time to time

When merging, bileto uses 'bzr missing' to determine who committed the commits in the source branch, in order to mark them as authors on the merge commit.

I know at least in the case of one MP being re-used (eg, if it's already merged and there's no unmerged commits left), then 'bzr missing' will report nothing and it will fail to attribute authors.

I've investigated the above case and it doesn't appear to be a re-used MP, so apparently there's some other unknown failure mode in which the 'bzr missing' code fails to identify authors.

I'm not sure why it's failing in this case but I have some hope that if I change the author-detection algorithm to one that doesn't rely on 'bzr missing', it may be possible to fix it in all cases, known and unknown.

Random idea: perhaps instead of using 'bzr missing' it should do 'bzr log' and just stop when it gets to the most recent tag. That way it would still discover authors even when the commits are already merged.

Another benefit of the 'bzr log' idea is that it would operate locally on the locally-branched branch, which would make it immune to network flakiness, which we sometimes see with 'bzr missing'

Also git branches branches locally before inspecting them so this should go away if everybody migrates to git ;-)

I believe this was fixed by the new MP-sorting algorithm, feel free to reopen if you see this again.