ci(build-and-test-differential): fetch only necessary commits (autowarefoundation#7468)

Signed-off-by: M. Fatih Cırıt <mfc@leodrive.ai>

Author: xmfcx

.github/workflows/build-and-test-differential-arm64.yaml

@@ -32,10 +32,14 @@ jobs:
             container: ghcr.io/autowarefoundation/autoware:latest-prebuilt
             build-depends-repos: build_depends.repos
     steps:
-      - name: Check out repository
+      - name: Set PR fetch depth
+        run: echo "PR_FETCH_DEPTH=$(( ${{ github.event.pull_request.commits }} + 1 ))" >> "${GITHUB_ENV}"
+
+      - name: Checkout PR branch and all PR commits
         uses: actions/checkout@v4
         with:
-          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: ${{ env.PR_FETCH_DEPTH }}
 
       - name: Show disk space before the tasks
         run: df -h

.github/workflows/build-and-test-differential.yaml

@@ -31,10 +31,14 @@ jobs:
             container: ghcr.io/autowarefoundation/autoware:latest-prebuilt
             build-depends-repos: build_depends.repos
     steps:
-      - name: Check out repository
+      - name: Set PR fetch depth
+        run: echo "PR_FETCH_DEPTH=$(( ${{ github.event.pull_request.commits }} + 1 ))" >> "${GITHUB_ENV}"
+
+      - name: Checkout PR branch and all PR commits
         uses: actions/checkout@v4
         with:
-          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: ${{ env.PR_FETCH_DEPTH }}
 
       - name: Show disk space before the tasks
         run: df -h