feat: Add Docker support and GitHub Container Registry CI/CD

[elasticdotventures]

• Add multi-stage Dockerfile for optimized container builds
• Add GitHub Actions workflow for building and pushing to ghcr.io
• Add docker-compose.yml for easy local development and testing
• Add comprehensive Docker usage documentation in docs/DOCKER.md
• Add .dockerignore to optimize build context

Features:

• Multi-platform support (linux/amd64, linux/arm64)
• Non-root container user for security
• Automatic semantic versioning and tagging
• Build provenance attestation
• Caching for faster builds
• Ready for MCP server integration

The container can be used as:

1. Standalone CLI tool in containerized environments
2. Base image for custom MCP server implementations
3. CI/CD integration for flashback operations

[Copilot]

Pull Request Overview

This PR adds comprehensive Docker support for Flashbacker, enabling containerized deployments and CI/CD automation through GitHub Container Registry. The implementation includes multi-stage builds for optimization, multi-platform support (amd64/arm64), security hardening with non-root user execution, and extensive documentation for various use cases including MCP server integration.

Key Changes:

• Multi-stage Dockerfile with build optimization and security best practices
• GitHub Actions workflow for automated building and publishing to ghcr.io with semantic versioning
• Docker Compose configuration for simplified local development and testing

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
Dockerfile	Multi-stage build setup with Node.js 22, non-root user (UID 1001), and optimized layer caching
.github/workflows/docker-build-push.yml	CI/CD workflow for multi-platform builds, GHCR publishing, and build attestation
docker-compose.yml	Local development setup with two service configurations for CLI and MCP server usage
.dockerignore	Build context optimization excluding unnecessary files like tests, docs, and build artifacts
docs/DOCKER.md	Comprehensive usage guide covering CLI usage, MCP integration, volume mounting, and deployment patterns

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[Copilot]

The attestation step references steps.build.outputs.digest, but the build step (line 63-76) doesn't have an id: build assigned to it. This will cause the attestation step to fail.

Add id: build to the "Build and push Docker image" step:

- name: Build and push Docker image
  id: build
  uses: docker/build-push-action@v5

[Copilot]

[nitpick] The .dockerignore file excludes lib/ (line 8), but the Dockerfile's runtime stage copies the built lib directory from the builder stage (line 39 in Dockerfile). Since the builder stage builds the project (line 21), this works correctly. However, excluding lib/ here could be confusing since it's explicitly copied in the Dockerfile.

Consider adding a comment to clarify:

# Build artifacts (built in Docker, not copied from host)
lib/

Suggested change

	# Build artifacts
	# Build artifacts
	# Build artifacts (built in Docker, not copied from host)

[Copilot]

[nitpick] The documentation uses the older docker-compose command syntax (with hyphen). While this still works, Docker Compose V2 (which is now bundled with Docker) uses docker compose (with a space) as the standard command.

Consider updating these examples to use the modern syntax:

# Run flashback commands
docker compose run --rm flashbacker flashback --version
docker compose run --rm flashbacker flashback init --mcp

Or add a note mentioning both syntaxes are supported.

[Copilot]

The command agent --context appears inconsistent with the flashback CLI commands shown elsewhere in the documentation (e.g., init, status, --version).

Please verify this is a valid flashback command. If agent is not a valid subcommand, this example should be updated to use an appropriate command for stdio MCP integration.

Suggested change

	agent --context
	init --mcp

[Copilot]

[nitpick] The version: '3.8' field in docker-compose.yml is deprecated as of Docker Compose v1.27.0 and is no longer required in Docker Compose V2. Modern best practice is to omit this field entirely.

Consider removing this line as it's no longer needed and the compose file will work without it.

Suggested change

version: '3.8'

[Copilot]

[nitpick] The workflow passes build arguments (BUILD_DATE, VCS_REF, VERSION) to the Docker build, but the Dockerfile doesn't declare these with ARG instructions or use them anywhere. These arguments will be silently ignored.

If these are intended to be used in the image (e.g., in labels), add them to the Dockerfile:

ARG BUILD_DATE
ARG VCS_REF
ARG VERSION

LABEL org.opencontainers.image.created="${BUILD_DATE}"
LABEL org.opencontainers.image.revision="${VCS_REF}"
LABEL org.opencontainers.image.version="${VERSION}"

Otherwise, remove the unused build-args from the workflow.

Suggested change

	build-args: |
	BUILD_DATE=${{ github.event.head_commit.timestamp }}
	VCS_REF=${{ github.sha }}
	VERSION=${{ steps.meta.outputs.version }}