fix(ci): improve macOS cache detection for Swatinem/rust-cache

[echobt]

Summary

This PR fixes the macOS CI cache detection issue. The macOS runner uses Swatinem/rust-cache@v2 (non-Blacksmith) which requires a different cache key strategy than the Blacksmith runners.

Problem

The macOS cache was not being detected/restored properly because:

1. The setup-cache job runs on Ubuntu (Blacksmith) and generates a cache key
2. macOS was using this pre-generated key with Swatinem/rust-cache@v2
3. Swatinem/rust-cache has different cache key composition than Blacksmith's cache

Solution

• Use consistent versioned prefix-key (v1-rust-test, v1-rust-build)
• Generate shared-key directly on macOS with matrix.name and hashFiles() for Cargo files
• This ensures the cache key is computed locally and includes OS-specific information

Changes

• Updated test job's non-Blacksmith cache configuration
• Updated build-check job's non-Blacksmith cache configuration

Testing

• macOS test job properly detects and restores cache (check job logs for "Cache restored")
• macOS build-check job properly detects and restores cache
• Ubuntu and Windows cache behavior remains unchanged

Notes

• The Test (ubuntu) job failure is a pre-existing flaky test (config::config_discovery::tests::test_caching) that also fails on main branch - not related to this PR's changes
• This PR only modifies .github/workflows/ci.yml and does not touch any Rust code

[greptile-apps]

Greptile Overview

Greptile Summary

This PR fixes macOS CI cache detection by changing how cache keys are computed for Swatinem/rust-cache@v2. Previously, macOS runners used cache keys generated on Ubuntu (from the setup-cache job), which caused cache misses because the OS-specific information didn't match. The fix computes cache keys locally on each runner using ${{ matrix.name }}-${{ hashFiles('**/Cargo.lock', '**/Cargo.toml') }}, ensuring proper OS-specific cache detection.

Changes:

• Updated test job: Changed prefix-key from rust-test-${{ matrix.name }} to versioned v1-rust-test and shared-key to locally-computed ${{ matrix.name }}-${{ hashFiles() }}
• Updated build-check job: Applied the same pattern change as test job
• Both changes only affect non-Blacksmith runners (macOS), not Ubuntu/Windows which use Blacksmith runners

Note: The same issue exists in .github/workflows/release.yml at lines 145-150 where macOS release builds also use the old pattern.

Confidence Score: 4/5

• This PR is safe to merge with minimal risk - it only changes cache configuration for macOS CI runners
• The changes are well-scoped to fix a specific cache detection issue. The logic is sound: computing cache keys locally with OS-specific information ensures proper cache hits. Confidence reduced by 1 point because the same issue exists in release.yml and should be addressed for consistency
• No files in this PR require special attention, but check .github/workflows/release.yml separately

Important Files Changed

Filename	Overview
.github/workflows/ci.yml	Updated macOS cache configuration to compute keys locally instead of using Ubuntu-generated keys; ensures proper cache detection with Swatimen/rust-cache@v2

Sequence Diagram

sequenceDiagram
participant Setup as setup-cache Job<br/>(Ubuntu Runner)
participant Ubuntu as test Job<br/>(Ubuntu Blacksmith)
participant macOS as test Job<br/>(macOS Runner)
participant Cache as GitHub Cache Storage
Note over Setup,Cache: BEFORE: Cache keys generated centrally on Ubuntu
Setup->>Setup: hashFiles() on Ubuntu
Setup->>Ubuntu: Output: rust-abc123
Setup->>macOS: Output: rust-abc123
Ubuntu->>Cache: Store: rust-test-ubuntu-rust-abc123
macOS->>Cache: Restore: rust-test-macos-rust-abc123
Cache-->>macOS: MISS - Key mismatch
Note over Setup,Cache: AFTER: Cache keys computed locally per OS
Setup->>Setup: hashFiles() on Ubuntu
Setup->>Ubuntu: Output: rust-abc123
Note over macOS: Computes key locally
Ubuntu->>Cache: Store: rust-test-ubuntu-rust-abc123
macOS->>macOS: hashFiles() + matrix.name
macOS->>Cache: Restore: v1-rust-test-macos-def456
Cache-->>macOS: HIT - Correct OS-specific key

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[greptile-apps]

_{1 file reviewed, 1 comment}

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[greptile-apps]

check that .github/workflows/release.yml at lines 145-150 also needs the same fix, as it has macOS runners using Swatinem/rust-cache@v2 with the old pattern (shared-key: ${{ needs.prepare.outputs.cache_key }})

Prompt To Fix With AI

This is a comment left during a code review.
Path: .github/workflows/ci.yml
Line: 136:137
Comment:
check that `.github/workflows/release.yml` at lines 145-150 also needs the same fix, as it has macOS runners using `Swatinem/rust-cache@v2` with the old pattern (`shared-key: ${{ needs.prepare.outputs.cache_key }}`)
How can I resolve this? If you propose a fix, please make it concise.