add support of COMPOSE_ENV_FILES env variable to pass a list of env files

[glours]

What I did
Add a new COMPOSE_ENV_FILES to allow users to define once the env files they want to associate to their Compose configuration
This PR will need a follow up PR in the doc repo to add the new env var cc @aevesdocker

Related issue
Internal discussion with Docker Captains

(not mandatory) A picture of a cute animal, if possible in relation to what you did

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (a345515) 57.55% compared to head (d286ef2) 57.54%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11061      +/-   ##
==========================================
- Coverage   57.55%   57.54%   -0.01%     
==========================================
  Files         129      129              
  Lines       11237    11241       +4     
==========================================
+ Hits         6467     6469       +2     
- Misses       4141     4144       +3     
+ Partials      629      628       -1     

Files	Coverage Δ
cmd/compose/compose.go	68.35% <100.00%> (+0.34%)	⬆️

... and 5 files with indirect coverage changes

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[nickjj]

Hi,

I'm not sure if this handles the use case described in the Docker Captains channel.

# docker-compose.yml
services:
  debian:
    image: "debian:bookworm-slim"
    restart: "${DOCKER_RESTART_POLICY:-unless-stopped}"

# .env
COMPOSE_ENV_FILES=.env,.env.local
DOCKER_RESTART_POLICY=yes

# .env.local
DOCKER_RESTART_POLICY=no

If you run docker compose config the value of restart is yes but it would be expected that it's no through the logic of:

• docker compose was called without explicitly defining any --env-file flags which means it will look for .env by default
• The new COMPOSE_ENV_FILES env var will be used which says to interpolate the .env file and then .env.local
  • This is the part that is failing the use case expectation
• no should be set

If you run COMPOSE_ENV_FILES=.env,.env.local docker compose config then everything works as expected but this requires altering your shell or creating a custom alias to run docker compose with that set. The original use case was to allow for running docker compose commands without modification.

Was this an accidental oversight or am I missing something?

[glours]

Hey @nickjj
I totally forgot to add the support via the .env files 🤦
Can you open a new issue to track it, please?

[nickjj]

No problem, here it is: #11122