For when you want newer mesa-vulkan-drivers builds than Debian packages!
Now including support for per-repository keyrings, bypassing the deprecated /etc/apt/trusted.gpg. Note that makes this script useless for Debian versions 10 or older, but older versions of this script using the apt-key add method will still work.
Install
Make the script executable and copy it to a PATH binary directory like /usr/local/bin.
Usage
Run with root privileges or sudo, passing the PPA as the only argument, e.g.:
sudo add-ppa-debian ppa:kisak/kisak-mesa
Updating expired keys
Simply rerun add-ppa-debian passing the affected PPA.
PPA Removal
Delete the PPA sources file from /etc/apt/sources.list.d/, optionally removing the PPA key file from /usr/share/keyrings/.