edgegap-containerize

Package any game server (Unreal, Godot, Node, Go, Rust, C++, a Unity build) into a Docker image that runs correctly on Edgegap, push it to the Edgegap Container Registry or Docker Hub, GHCR, ECR, GCR or GitLab, and register it as an app version: the container contract, Dockerfile patterns, linux/amd64 builds on Apple Silicon, image tags, registry credentials on the version, and port mapping. Use whenever writing or fixing a Dockerfile for a game server, building on a Mac, pushing to registry.edgegap.com, getting "unable to pull image" or exec format errors, or when someone asks how to get a server build onto Edgegap. Engine-agnostic; edgegap-unity has a ready Unity Dockerfile.