fix(composer): warn that global and self-update changes don't persist, use stable for empty composer_version, fixes #7993

[stasadev]

The Issue

• Fixes Document how to update Composer to latest release #7993

DDEV users don't know why the ddev composer self-update is not saved on ddev restart. This is a common behavior in Docker when you modify something outside of bind mounts (i.e. outside the project directory), but people don't know about it.

How This PR Solves The Issue

• Shows a warning for ddev composer self-update, ddev composer selfupdate, ddev composer global with a link to the docs.

• Improves documentation.

• composer_version: "" used composer_version: "2" under the hood, but docs say https://docs.ddev.com/en/stable/users/configuration/config/#composer_version

  Can be 2, 1, or empty ("") for latest major version at container build time.

  composer_version: "" is now the same as composer_version: "stable"

Manual Testing Instructions

Updated docs:

• https://ddev--7995.org.readthedocs.build/en/7995/users/configuration/config/#composer_version
• https://ddev--7995.org.readthedocs.build/en/7995/users/usage/developer-tools/#composer-limitations

New warning:

$ ddev composer global require psr/log
Composer global changes do not persist across DDEV restarts.
See https://docs.ddev.com/en/stable/users/usage/developer-tools/#composer-limitations for details.
Changed current directory to /home/stas/.composer
./composer.json has been created
...

$ ddev composer self-update
Composer self-update changes do not persist across DDEV restarts.
See https://docs.ddev.com/en/stable/users/usage/developer-tools/#composer-limitations for details.
You are already using the latest available Composer version 2.9.3 (stable **channel).**

Testing composer_version: "" (--2 -> --stable):

$ ddev config --composer-version=
$ ddev start
$ cat .ddev/.webimageBuild/Dockerfile | grep composer
### DDEV-injected composer update
RUN export XDEBUG_MODE=off; composer self-update --stable || composer self-update --stable || true; composer self-update --2 || log-stderr.sh composer self-update --2 || true

-RUN export XDEBUG_MODE=off; composer self-update --stable || composer self-update --stable || true; composer self-update --2 || log-stderr.sh composer self-update --2 || true
+RUN export XDEBUG_MODE=off; composer self-update --stable || composer self-update --stable || true; composer self-update --stable || log-stderr.sh composer self-update --stable || true

Automated Testing Overview

Release/Deployment Notes

[github-actions]

Download the artifacts for this pull request:

• all-ddev-executables.zip
• ddev-macos-amd64.zip
• ddev-macos-arm64.zip
• ddev-linux-arm64.zip
• ddev-linux-amd64.zip
• ddev-windows-amd64.zip
• ddev-windows-amd64-installer.zip
• ddev-windows-arm64.zip
• ddev-windows-arm64-installer.zip

See Testing a PR.

[rfay]

Looks good to me. Probably more than most people need to know, but helps with full response to the (very) occasional support question.

[stasadev]

I think some people have ddev composer self-update in post-start hooks, so this very detailed explanation should help.