Introduce an option "--omit-merges" for "bzr log".
This will omit the merging commits themselves, i.e. commits with more than a single parent. The idea is that these commits tend to describe the mechanics of code development, but are at best only summaries of the work done in sidelines. So omitting them but including the sidelines will print all the commits that actually contributed features to the code, without too much noise and duplicate information. This is particularly useful when generating change logs for websites or tarballs.