Fix swift-format workflow with best practices

- Add ref parameter to checkout to address detached HEAD warning
- Add git safe.directory configuration
- Replace cache with separate cache/restore and cache/save steps
- Use static cache key instead of dynamic hashFiles key
- Fixes deprecation warnings and improves reliability

Author: coenttb

.github/workflows/swift-format.yml

@@ -17,20 +17,25 @@ jobs:
       contents: write
     steps:
       - uses: actions/checkout@v5
+        with:
+          ref: ${{ github.head_ref || github.ref_name }}
+
+      - name: Configure git safe directory
+        run: git config --global --add safe.directory $PWD
 
       - uses: swift-actions/setup-swift@v2
         with:
           swift-version: '6.0'
 
-      - name: Cache swift-format
-        id: cache-swift-format
-        uses: actions/cache@v4
+      - name: Restore swift-format cache
+        id: cache-swift-format-restore
+        uses: actions/cache/restore@v4
         with:
           path: .build/swift-format
-          key: ${{ runner.os }}-swift-format-${{ hashFiles('.github/workflows/swift-format.yml') }}
+          key: ${{ runner.os }}-swift-format-main-v1
 
       - name: Build swift-format
-        if: steps.cache-swift-format.outputs.cache-hit != 'true'
+        if: steps.cache-swift-format-restore.outputs.cache-hit != 'true'
         run: |
           git clone --depth 1 --branch main https://github.com/apple/swift-format.git
           cd swift-format
@@ -47,3 +52,10 @@ jobs:
         with:
           commit_message: Run swift-format
           branch: 'main'
+
+      - name: Save swift-format cache
+        uses: actions/cache/save@v4
+        if: steps.cache-swift-format-restore.outputs.cache-hit != 'true'
+        with:
+          path: .build/swift-format
+          key: ${{ runner.os }}-swift-format-main-v1