Add example Dockerfile and docker-compose

[tomny-dev]

Summary

• add minimal Dockerfile
• add example docker-compose.yml
• expand README with build and compose instructions

Testing

• git status --short

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https://chatgpt.com/codex/tasks/task_e_687ff4e5cf008328bc53210ac6c19693

[gemini-code-assist]

Summary of Changes

Hello @tomny-dev, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces foundational Docker support to the docker-template project by adding a Dockerfile and a docker-compose.yml example. My aim is to provide a quick and easy way for users to containerize and run the application, enhancing its portability and ease of setup. The accompanying README.md updates ensure that these new features are well-documented and accessible.

Highlights

• Docker Support: I've added a minimal Dockerfile to enable containerization of the project, using Alpine Linux as the base image and setting a simple 'Hello' command.
• Docker Compose Integration: I've included an example docker-compose.yml file, allowing users to easily build and run the application's Docker image using docker compose up.
• Documentation Update: The README.md has been expanded to provide clear instructions on how to build the Docker image and run the application using Docker Compose, making it easier for new users to get started.

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[gemini-code-assist]

Code Review

The PR adds a basic Dockerfile, docker-compose.yml, and updates the README.md to provide an example of containerizing an application. The changes are a good starting point. My review focuses on incorporating Docker and Docker Compose best practices to improve security, reproducibility, and maintainability. Key suggestions include pinning the base image version, running the container as a non-root user for security, and refining the docker-compose.yml to align with modern standards and avoid anti-patterns like hardcoding container names. I've also suggested a small improvement to the README.md to make the instructions more complete for users.

[gemini-code-assist]

Running containers as a non-root user is a critical security best practice. The container will run as the root user by default, which should be avoided to limit the potential blast radius of a vulnerability.

Please add instructions to create a non-root user and switch to it before the CMD instruction. For example:

RUN addgroup -S appgroup && adduser -S appuser -G appgroup
USER appuser

[gemini-code-assist]

Hardcoding container_name is generally considered an anti-pattern in Docker Compose. It prevents you from scaling a service (e.g., docker compose up --scale app=3), as container names must be unique.

It's better to let Docker Compose manage container names automatically. I recommend removing this line to follow best practices and allow for scalability.

[gemini-code-assist]

For reproducible builds, it's a best practice to pin the base image to a specific version instead of using a floating tag like :3. This prevents unexpected changes or build failures when the base image is updated.

Consider using a more specific tag, for example alpine:3.19.

FROM alpine:3.19

[gemini-code-assist]

It's common to run services in the background using detached mode (-d). Additionally, it would be very helpful for users to know the command to stop and clean up the created resources.

Consider also mentioning docker compose down in the instructions.

Suggested change

	docker compose up
	docker compose up -d

[gemini-code-assist]

The top-level version property is deprecated in modern Docker Compose files and is no longer necessary. You can safely remove this line.