When additional repos are configured, apt upgrade

If one has set apt-setup/{DEVEL,local*}/repository then they will not be used during base-installer's debootstrap because debootstrap does not support multiple repos, so if the reason you specified the extra repo(s) was in the hope of modifying the behaviour of the installer after base-installer, it won't currently work.

This adds a script that checks for those settings, and if present does an apt update & upgrade in order to pull in higher versioned packages that are available from the additional repos.

It also checks if any of the extra repos have https urls, and if so also installs ca-certificates so that the downloads don't fail with untrusted certificate warnings

Of course, it would be nicer to do this in debootstrap to avoid the scanario where debootstrap installs an old version, which is then replaced with a newer version from the extra repo, but at least this gets the version you wanted to install in the end.

BTW this lets one test things like blendsel more easily.