Use cat << EOF to automatically derive suite from /etc/os-release

[erickeller]

No need to find out the suite for Ubuntu/Debian like system.
using a single sed operation would give the suite, combined with cat << EOF it can be written to the destination file.
The goal of this MR is to simplify the installation on Debian like OS.

[CLAassistant]

All committers have signed the CLA.

[jef-n]

won't work on sid.

[agiudiceandrea]

I guess it won't work also on Linux Mint.

[erickeller]

won't work on sid.

you are right as the sid currently points to a codename forky:

docker run -ti --rm debian:sid sed -n "s/VERSION_CODENAME=\(.*\)/\1/p" /etc/os-release
Unable to find image 'debian:sid' locally
sid: Pulling from library/debian
63fb544511bd: Pull complete 
Digest: sha256:a4bd9c028b6289c6edcf61b9101de4cf8bb48b2d441139689dd1bd780a7b000b
Status: Downloaded newer image for debian:sid
forky

and your repository dists are labeing it sid -> https://debian.qgis.org/debian/dists/sid/

so I would update the oneliner to: . /etc/os-release; [ "$ID" = "debian" ] && grep -q "/sid" /etc/debian_version && echo "sid" || echo "${UBUNTU_CODENAME:-$VERSION_CODENAME}"

But this would also work for all the above mentioned distribution including sid oldoldstable oldstable and mint

@agiudiceandrea I just installed Linux Mint to ensure it also works there.

I will upate the PR with his one-liner