Comment 40 for bug 2033308

> d) regarding saving the preferences backup in etc/apt/preferences.d.save, and the "risk" of not cleaning up and leaving this directory there

Since /etc/apt/preferences.d.save is what is used in the mantic live-build, I feel like it makes most sense to keep the same temporary folder on backport to the older releases. I also experimented this morning with using /tmp instead of /etc/apt and the restore does not work; it seems that something between the backup and restore clears out /tmp.

> b) given the uncertainty around the motivation for the original removal of all preferences files during the build, have you tested building an image with and without the fix, and compared them? Could this be added to the test plan, to make sure the fix is not inadvertently introducing other changes?

I added notes for building patched and unpatched images to the Test Plan and comparing filelists and manifests.