chore: set debian_default to trixie in config

[MikeMcC399]

• closes update.sh fails to update with pruned variants #2438

Description

In config, change the entry default_variant:

From	To
bookworm (Debian 12)	trixie (Debian 13)

Motivation and Context

default_variant is used in the following code to determine whether a Node.js version directory is valid or not:

docker-node/functions.sh

Lines 152 to 156 in 3b32380

	for dir in "${dirs[@]}"; do
	if [ -e "${dir}/Dockerfile" ] || [ -e "${dir}/${default_variant}/Dockerfile" ]; then
	versions+=("${dir#./}")
	fi
	done

To allow for the flexibility of dropping bookworm (Debian 12) from the configuration at some later stage, the default_variant is updated to trixie.

Without this change, a Node.js version configuration that does not include bookworm would be ignored. (See issue #2438.)

bookworm (Debian 12) already transitioned into end-of-life on 2026-06-10 and is now in its LTS stage with reduced architectural support. See also issue #2556.

Testing Details

Make temporary changes:

rm -rf 26/bullseye*

Edit versions.json to temporarily remove bullseye & bullseye-slim from Node.js 26.

Execute ./update.sh.

Confirm that the logs show Node.js 26 being updated.

Test logs

$ ./update.sh
Updating version 22...
Updating version 24...
Updating version 26...
26/trixie/Dockerfile updated!
24/bookworm/Dockerfile updated!
24/trixie/Dockerfile updated!
22/bookworm-slim/Dockerfile updated!
22/trixie/Dockerfile updated!
22/trixie-slim/Dockerfile updated!
26/bookworm/Dockerfile updated!
24/bullseye/Dockerfile updated!
22/bullseye-slim/Dockerfile updated!
26/bookworm-slim/Dockerfile updated!
26/trixie-slim/Dockerfile updated!
22/bullseye/Dockerfile updated!
24/trixie-slim/Dockerfile updated!
24/bullseye-slim/Dockerfile updated!
22/bookworm/Dockerfile updated!
24/bookworm-slim/Dockerfile updated!
26/alpine3.23/Dockerfile updated!
24/alpine3.24/Dockerfile updated!
22/alpine3.23/Dockerfile updated!
22/alpine3.24/Dockerfile updated!
26/alpine3.24/Dockerfile updated!
24/alpine3.23/Dockerfile updated!
Done!

Types of changes

• Documentation
• Version change (Update, remove or add more Node.js versions)
• Variant change (Update, remove or add more variants, or versions of variants)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (none of the above)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• All new and existing tests passed.

[MikeMcC399]

This PR should have no effect on the current Dockerfile builds, since each of the Node.js releases includes both bookworm and trixie.

It only comes into play if bookworm were to be dropped from any Node.js release line's configuration, so this is a non-urgent PR.

[sxa]

Seems reasonable to me - I wouldn't expect any negative side effects from this although it would be good if at least one other person could approve too before merging :-)

[MikeMcC399]

@sxa

Thanks! I'll leave it for @nschonni to cross-check (or anyone else with in-depth insight into the script workings). No urgency to merge.