Comment 3 for bug 202420

Here's the canonical use case:

Jono is working on Feature X (codename "Infinite Jest"), a really big feature that requires significant refactoring of the project codebase. To make life easier for his reviewer, Jono has made a branch called 'feature-x-refactor' that does the refactoring, and another branch called 'feature-x-itself' that adds the feature and depends on feature-x-refactor.

Jono submits a proposal to merge feature-x-refactor and then submits another proposal to merge feature-x-itself, which depends on feature-x-refactor landing first.

In a future release of Launchpad, the merge proposal page will display diffs. When this happens, the feature-x-refactor merge page will show the diff you get when you merge feature-x-refactor into trunk, and the feature-x-itself page will show the diff you get when you first merge *feature-x-refactor* into trunk, commit, then merge feature-x-itself.

This means that reviewers of feature-x-itself can concern themselves with the changes in that branch, rather than the changes in the refactoring branch.