092: Fsops coverage hardening

Status: Accepted
Date: 2026-01-17
Context:
- The workspace requires at least 90% per-crate line coverage (ADR 091).
- revaer-fsops contained untested branches in pipeline helpers and filesystem routines.
Decision:
- Add targeted unit tests for fsops pipeline steps, rule parsing, and file operations.
- Keep all test-only logic inside #[cfg(test)] modules.
- Alternatives considered: integration tests backed by RuntimeStore + database; rejected for higher cost and slower feedback.
Consequences:
- Positive outcomes:
  - Improved coverage and regression protection for fsops edge cases.
- Risks or trade-offs:
  - Additional filesystem IO during tests; mitigate with temp dirs and deterministic fixtures.
Follow-up:
- Run just cov and just ci to confirm the per-crate gate.
- Watch for platform-specific permission semantics in CI.

Motivation

Raise revaer-fsops coverage to meet the 90% per-crate gate while strengthening confidence in filesystem post-processing edge cases.

Exercise both happy-path and skip/error branches without introducing production-only hooks.
Favor direct unit tests of helper functions to keep the tests fast and deterministic.

Added unit tests for meta initialization, allowlist enforcement, glob parsing errors, archive extension checks, step short-circuiting, and file operation paths.
Added permission/ownership tests for unix targets to cover apply_permissions, resolve_owner, and resolve_group.

None; no runtime behavior changes.

Risk: file-permission tests may behave differently on non-unix systems.
Rollback: revert the added tests and rework with platform guards if CI shows instability.

No new dependencies added. Alternative considered: integration coverage via database-backed runtime store, rejected due to setup overhead.