Summary

Complete rewrite of Initium from Go to Rust, reducing Docker image size by 76%.

What changed

Language & Toolchain

• Go 1.25 → Rust 1.85 (musl static linking)
• cobra → clap for CLI
• Go text/template → minijinja (Jinja2-style) for template rendering
  Binary / Image Size
  | | Go | Rust | Reduction |
  |---|---|---|---|
  | Docker image (scratch) | ~7.4 MB | 1.83 MB | 76% |
  All 6 subcommands reimplemented:
• wait-for — TCP + HTTP/HTTPS with retries, backoff, jitter
• migrate — command exec with lock-file idempotency
• seed — command exec with structured logging
• render — envsubst + Jinja2 templates (via minijinja)
• fetch — HTTP fetch with auth, TLS, retry
• exec — arbitrary command with workdir
  CI/CD updated:
• CI: cargo test + clippy + rustfmt
• Release: Rust toolchain, same Docker buildx multi-arch flow
• Both Dockerfiles (scratch + jyq) rewritten for Rust
  Docs updated:
• design.md: Rust architecture, directory structure, how-to-add-subcommand
• usage.md: template mode → Jinja2
• README.md, FAQ.md: image sizes, tool references
• CHANGELOG.md: Rust rewrite entry
• tests/README.md: cargo test references

Test results

test result: ok. 36 passed; 0 failed; 0 ignored

How to verify

cargo test          # 36 tests pass
cargo build --release
./target/release/initium --help
docker build -t test -f Dockerfile .
docker run --rm test --version

Breaking changes

• Template mode gotemplate now uses Jinja2 syntax: {{ env.VAR }} instead of {{.VAR}}
• Build requires Rust toolchain instead of Go