docker-entrypoint.sh: enable XTRACE if ENTRYPOINT_XTRACE environment …

[jan-matejka]

…variable is non-empty

[tianon]

I usually just do docker run ... bash -x docker-entrypoint.sh ... when I need this 😅

[jan-matejka]

I usually just do docker run ... bash -x docker-entrypoint.sh ... when I need this 😅

1. That will not be effective through exec gosu ...
2. GHA do not allow to override CMD from argv so you have to build a custom image for that.

[tianon]

The simplest workaround for 1. is to use --user (which is a good idea anyhow), and the simplest workaround for 2. is to use run: docker run ... instead of https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#jobsjob_idservices (which is just combining the YAML arguments into a docker run command for you).