feat: implement GitHub to Forgejo/Codeberg repository mirroring

[guilycst]

Summary

Implements gitmeout - a Go CLI tool that mirrors repositories from GitHub to Forgejo/Codeberg instances.

Features

• Mirror types: Supports both push and pull mirrors
  • Push mirrors: Clone from source, push --mirror to target (for Codeberg)
  • Pull mirrors: Use Forgejo MigrateRepo API (for vanilla Forgejo instances)
• Filtering:
  • Personal repos (default)
  • Organization repos
  • Explicit repo list with owner/* wildcard support
• Graceful shutdown: Context cancellation support
• Multiarch Docker: linux/amd64, linux/arm64
• CI/CD: GitHub Actions for testing and releases
• Kubernetes: Job and CronJob manifests

Configuration

YAML config with environment variable interpolation:

source:
  type: github
  token: ${GITHUB_TOKEN}
  filters:
    personal: true
    orgs: []
    repos: []

targets:
  - name: codeberg
    type: forgejo
    url: https://codeberg.org
    token: ${CODEBERG_TOKEN}
    mirror_type: push
  - name: decastro
    type: forgejo
    url: ${DECASTRO_URL}
    token: ${DECASTRO_TOKEN}
    mirror_type: pull

Files Added

• .github/workflows/ci.yml - CI pipeline (test, lint)
• .github/workflows/release.yml - Release pipeline (binaries + Docker multiarch)
• cmd/gitmeout/main.go - Entry point
• internal/config/ - YAML config parsing with env interpolation
• internal/git/client.go - Git clone/push operations
• internal/mirror/service.go - Core mirroring logic
• internal/source/github/client.go - GitHub API client
• internal/target/forgejo/client.go - Forgejo API client
• deploy/k8s/ - Kubernetes manifests

Testing

All tests passing:

✓ 25 tests in 6 packages

Tested locally with both push (Codeberg) and pull (vanilla Forgejo) mirrors.