better review of package changes

When packages are changed and proposed as a merge in launchpad, it can be hard to tell whats going on.

This is a complex topic, and will be getting discussed at UDS I hear.

This bug may need to be split into smaller ones, but acking the issue is a good start.

Both launchpad-code and bzr need to make it easier for distro developer accepting a change to assess whether the change is right. There are many sorts of changes people submit, and some are pretty easy to work with:
 - cherrypicked fixes from upstream
 - small changes to packaging or upstream

Others are harder:
 - new upstream releases (we don't usually want to audit those changes)
 - debian accepting ubuntu changes, with the changelog merging badly [this looks particularly ugly]
 - patches to patches (e.g. a patch to fix a bug wasn't quite right)

Looms may help with this, but unless we had everything in looms it wouldn't be better; there will be a branch->loom importer in bzr-builddeb at some point.

I'm filing a separate bug for using the bzr-builddeb changelog merge on launchpad, which should help today.