Repair wp/5.6 branch Actions: Add a WP_ENV_MARIADB_VERSION environment variable - #575

What?

Adds a WP_ENV_MARIADB_VERSION environment variable that chooses the MariaDB version wp-env uses. The database image in packages/env/lib/build-docker-compose-config.js changes from 'mariadb' to 'mariadb:${WP_ENV_MARIADB_VERSION:-latest}'. When the variable isn't set, the image resolves to mariadb:latest, the same image as before.

The README gets a note next to the existing port-variable note. Besides the variable, it says that MariaDB cannot start on a database written by a newer version, so before switching to a lower version, run wp-env destroy, which removes the environment's Docker containers, volumes, networks, and local files, not only the database. It also says that with a version older than 11.4, wp db commands in the cli and tests-cli containers fail and wp-env clean leaves the database as it is: the MariaDB client in the wordpress:cli image requires TLS, and MariaDB servers before 11.4 do not offer it. WordPress itself is not affected.

packages/env/CHANGELOG.md gets an entry under Unreleased → New Features.

Why?

This branch's wp-env (2.1.0) always runs the floating mariadb image, which today is a MariaDB release many years newer than anything this branch was tested against. There is currently no way to pin an older, era-appropriate version for testing.

How?

This follows #83751, which adds a mariadbVersion option and WP_ENV_MARIADB_VERSION environment variable to trunk. wp-env 2.1.0 has no version settings to extend, so only the environment variable is ported. Docker Compose fills it in when it reads the generated docker-compose.yml, the same way this file already uses WP_ENV_PORT/WP_ENV_TESTS_PORT in the port mappings and LOCAL_PHP in the phpunit image.

This branch's wp-env runs one mysql service for both the development and tests environments, so a single image line changes.

A new test in packages/env/test/build-docker-compose-config.js checks the generated image string. npm run test-unit -- packages/env passes all 63 tests locally. (packages/env/test/cli.js couldn't load locally because nodegit's native module wasn't built; that's unrelated to this change.)

Pinning the version doesn't by itself fix the mariadb-check TLS error that wp-env start can hit on this branch; that is a separate problem.

Use of AI Tools

This PR was created by Claude Code under my supervision. All code should be treated as AI-produced and not yet reviewed by a human until this PR is marked Ready for Review.