cross-platform-shelllisted

# Cross-Platform Shell Guidelines This repo's shell entrypoints (`xuunity_light_unity_mcp.sh`, `templates/run.sh`, `scripts/testing/*.sh`) are executed on macOS, Linux, and Windows Git Bash. Every rule below was earned from a real silent-hang incident on Windows CI. Violating them produces hangs with zero output that eat the whole CI job time limit. --- ## 1. Path Walks Terminate on a Fixed Point, Never on `/` On Windows, `pwd`/paths can take forms like `D:/a/repo` or `D:\a\repo`. A `dirname` descent walks `D:/a → D: → . → .` and **never reaches `/`** — the loop spins forever inside `$(...)` with no output. ```bash # INCORRECT (infinite loop on Windows path forms) while [[ "$candidate" != "/" ]]; do candidate="$(dirname "$candidate")" done # CORRECT (terminates on any path form: /, //, D:, .) local previous_candidate="" while [[ -n "$candidate" && "$candidate" != "$previous_candidate" ]]; do previous_candidate="$candidate" candidate="$(dirname "$candidate")" done ``` ## 2. Resolve Git Bash Explicitly When Spawning From Native Code `subprocess.run(["bash", ...])` from Python on Windows resolves through CreateProcess search order to the **System32 WSL stub**, not Git Bash. Use `tests/bash_support.py:resolve_bash_executable()` — it prefers `Git/usr/bin/bash.exe` (the real binary) over the `Git/bin` shim, which also makes process-tree kill reliable. ## 3. No `xargs -P` Under MSYS Parallel `xargs` is unreliable under MSYS fork emulation (known upstream hangs). The