Hi,

I very often need to run autopkgtest of the package just built,
with external additional debs, something like

autopkgtest ../node-undici_7.15.0+dfsg+~cs3.2.0-1_amd64.changes --copy=../debs:/root/debs --setup-commands="apt install -y /root/debs/*.deb" --apt-upgrade -- unshare --release unstable --arch amd64

It would be awesome to have a "debautopkgtest" or "debtest" helper that would simply run this command,
with the right values when used inside a package directory that's just been built.

Also, a --extra-package flag, with the same semantics as sbuild's, would be incredibly useful (--copy + --setup-commands is not user-friendly).

Thanks !
Jérémy