Comment 14 for bug 645404

@carlfk, can you elaborate on:

> deploy a private key (or similarly sensitive secret) file and a publicly
> readable script (apt-add-repository...) and it just runs, no browser,
> no user, no typing

for a private ppa, the script will only generate 3 files (e.g. for ppa:ddstreet/private on disco):
1) /etc/apt/sources.list.d/ddstreet-ubuntu-private-disco.list
2) /etc/apt/auth.conf.d/ddstreet_ubuntu_private.conf
3) /etc/apt/trusted.gpg.d/ddstreet_ubuntu_private.gpg

you could just copy those directly to whatever system you want, and not have to run anything at all on the system (besides 'sudo apt update' and then upgrade/install). Are you asking for something different?