feat(devcontainer): add Dev Container configuration for reproducible …

[Princess0407]

Description

Right now, getting started with urunc requires manually installing Docker, QEMU, containerd, CNI plugins, and Go across different package managers and manual steps. This is documented in the installation guide, but it's a significant barrier for new contributors and LFX mentees who just want to run make unittest or make lint.
A Dev Container automates that same setup into a reproducible, version controlled environment.

What's added

• .devcontainer/devcontainer.json : configures the container with Docker in Docker, KVM passthrough (--device=/dev/kvm), and VS Code extensions for Go development
• .devcontainer/Dockerfile : Ubuntu 22.04 base image with Go, QEMU, containerd, CNI plugins, and build tools pre installed
• .devcontainer/post-create.sh : runs after container creation to set up git safe directory and download Go modules

How to use it

Local VS Code + Docker (recommended for full e2e testing):

1. Install the Dev Containers extension in VS Code
2. Open the project and run "Dev Containers: Reopen in Container"
3. The container gets KVM access, so VM based e2e tests can work if VMMs are installed manually

GitHub Codespaces:

• Supports make unittest, make lint, and build workflows
• e2e tests that spawn VMs (Firecracker/QEMU) are not available because Codespaces standard instances don't support nested virtualization/KVM

Verification

Tested locally with docker build and docker run:

docker build -f .devcontainer/Dockerfile -t urunc-dev-test .
docker run --rm -it -v $(pwd):/workspace -w /workspace urunc-dev-test bash

Test results

make unittest was run inside the dev container. The test suite passes overall with 3 pre existing failures that are unrelated to this PR:

Failing test	Reason
TestCopyFile/copy_file_target_dir_creation_failed	Test expects mkdir to fail with permission denied, but root can create any directory
TestCopyFile/copy_file_target_file_creation_failed	Test expects read-only filesystem error, but root ignores read-only flags
TestMoveFile/move_file_target_file_creation_failed	Same read only filesystem assumption fails under root

These failures occur whenever tests run as root (which the dev container does) and are not introduced by this PR. They are existing issues in pkg/unikontainers/utils_test.go.

Inside container:

bash .devcontainer/post-create.sh
make unittest   
make lint       

Related

Fixes #953

[netlify]

✅ Deploy Preview for urunc canceled.

Name	Link
🔨 Latest commit	6e40190
🔍 Latest deploy log	https://app.netlify.com/projects/urunc/deploys/6a80a82e69d6af0008585b4a