Simplify changed files check

.github/workflows/pr.ci.js.yml

@@ -10,7 +10,8 @@ jobs:
     runs-on: ubuntu-22.04
 
     steps:
-      - uses: actions/checkout@v3
+      - name: Checkout PR
+        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
         with:
           fetch-depth: ${{ github.event_name == 'pull_request' && 2 || 0 }}
       - name: Get changed files
@@ -21,8 +22,6 @@ jobs:
           else
               echo "changed_files=$(git diff --name-only --diff-filter=ACM ${{ github.event.before }} ${{ github.event.after }} | xargs)" >> $GITHUB_OUTPUT
           fi
-      - name: Checkout PR
-        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
 
       - name: Use Node.js LTS (20.x)
         uses: actions/setup-node@1e60f620b9541d16bece96c5465dc8ee9832be0b
@@ -45,6 +44,16 @@ jobs:
     steps:
       - name: Checkout PR
         uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
+        with:
+          fetch-depth: ${{ github.event_name == 'pull_request' && 2 || 0 }}
+      - name: Get changed files
+        id: changed-files
+        run: |
+          if ${{ github.event_name == 'pull_request' }}; then
+              echo "changed_files=$(git diff --name-only --diff-filter=ACM -r HEAD^1 HEAD | xargs)" >> $GITHUB_OUTPUT
+          else
+              echo "changed_files=$(git diff --name-only --diff-filter=ACM ${{ github.event.before }} ${{ github.event.after }} | xargs)" >> $GITHUB_OUTPUT
+          fi
 
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@1e60f620b9541d16bece96c5465dc8ee9832be0b
@@ -55,11 +64,7 @@ jobs:
         run: yarn install --immutable
 
       - name: Run exercism/typescript ci (runs tests) for changed/added exercises
-        run: |
-          PULL_REQUEST_URL=$(jq -r ".pull_request.url" "$GITHUB_EVENT_PATH")
-          curl --url $"${PULL_REQUEST_URL}/files?per_page=100" --header 'authorization: Bearer ${{ secrets.GITHUB_TOKEN }}' | \
-            jq -c '.[] | select(.status == "added" or .status == "modified") | select(.filename | match("\\.(js|jsx|ts|tsx|md|json)$")) | .filename' | \
-            xargs -r yarn node scripts/pr.mjs
+        run: yarn node scripts/pr.mjs ${{ steps.changed-files.outputs.changed_files }}
 
   impersonate:
     # This job tries to run tests for the 'hello-world' exercise, but