Copilot instructions for `prek`

Code requirements

Concise, idiomatic Rust (2024 edition).
Proper error handling (no unwraps, panics, etc. in app code).
Clear separation of concerns (e.g., config parsing vs. execution).
Thorough test coverage (unit + integration tests, snapshot testing where appropriate).

Rust workspace under crates/*. The main CLI binary is crates/prek (src/main.rs).
prek is a Rust reimplementation of pre-commit: configuration parsing lives in crates/prek/src/config.rs, execution/dispatch is in crates/prek/src/run.rs, and integration tests exercise the CLI end-to-end under crates/prek/tests/.
User-facing output is centralized:
- Warnings go through warn_user! / warn_user_once! in crates/prek/src/warnings.rs (can be disabled via -q / -qq).
- Progress/output selection is via Printer in crates/prek/src/printer.rs.
Cross-process coordination uses a store under $PREK_HOME (see Store::from_settings / Store::lock_async in crates/prek/src/store.rs).

Lint/format like CI: mise run lint (runs cargo fmt + cargo clippy --all-targets --all-features --workspace -- -D warnings).
Run all tests: mise run test (workspace, all targets/features).
Snapshot-first test workflow (insta):
- Unit/bin tests with review UI: mise run test-unit -- <filter> or mise run test-all-unit.
- Integration tests with review UI: mise run test-integration <test> [filter] or mise run test-all-integration.
- Snapshots live under crates/prek/src/snapshots/ and are used heavily by tests in crates/prek/tests/.

Prefer fs-err / fs-err::tokio over std::fs / tokio::fs for filesystem operations (see many modules, e.g. crates/prek/src/store.rs).
Prefer anyhow::Result for app-level flows and thiserror for typed errors when there’s a clear domain (see crates/prek/src/store.rs).
Logging uses tracing; default behavior is configured in crates/prek/src/main.rs and can be overridden via RUST_LOG.
CLI is defined with clap under crates/prek/src/cli/ (entry in crates/prek/src/cli/mod.rs). If adding a command, keep wiring consistent with existing cli/* modules.

Integration tests use TestContext helpers in crates/prek/tests/common/mod.rs and snapshot macros like cmd_snapshot!.
Tests often normalize paths with regex filters; prefer using context.filters() for stable snapshots.
DO NOT run whole-workspace tests in CI; they are slow. Use cargo test -p prek --lib <unit-test> -- --exact (or cargo test -p prek --bin prek <unit-test> -- --exact) for unit tests and cargo test -p prek --test <test> -- <filter> for integration tests.
Use cargo insta review --accept to accept snapshot changes after running tests locally.

Docs are built with MkDocs (see mkdocs.yml); run locally via mise run build-docs.
CLI reference + JSON schema are generated via mise run generate (see tasks in mise.toml).

If a change affects user-visible output, update the relevant snapshot(s) under crates/prek/tests/ (use the cargo insta review flow).
Keep output stable and routed through existing printer/warning macros rather than printing directly.