feat: add env-file input for compose interpolation

[defangdevs]

Migrated from #51 so the source branch lives in the upstream repository. Earlier discussion and reviews remain on the original PR.## What

Adds an env-file input so workflows can point Compose interpolation at a non-default environment file (e.g. .env.production), matching docker compose --env-file.

The input is mapped to the COMPOSE_ENV_FILES environment variable that the Defang CLI reads (whitespace-delimited input is converted to the comma-separated form the CLI expects), the same way project maps to COMPOSE_PROJECT_NAME. Using the env var means it applies to whatever command runs, not just compose up.

Depends on the CLI-side support in DefangLabs/defang#2178.

Usage

- uses: DefangLabs/defang-github-action@v2
  with:
    env-file: ".env.production"        # or: ".env .env.production"

Changes

• action.yaml: new env-file input; set COMPOSE_ENV_FILES in the env-setup step.
• README.md: new "Using an Environment File" section.
• .github/workflows/test.yaml + test/compose.envfile.yaml + test/action.env: a step that runs compose config with env-file and asserts the interpolated value reaches the CLI output.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Sw7j9FYnbChZJbYArxbhuo

Summary by CodeRabbit

• New Features

  • Added optional deployment summaries with a services table and primary HTTPS endpoint output.
  • Added an optional env-file input for deployment environment files.
  • Supports multiple space-separated files, with later files overriding earlier values.
  • Environment files can be configured in YAML, with .env behavior documented.
  • Output capture is now disabled by default.

• Tests

  • Added deployment coverage verifying environment variables load correctly from specified files.

[coderabbitai]

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