try github.event variables

as recommended here https://github.com/orgs/community/discussions/25797#discussioncomment-3249294

.github/workflows/push.yml

@@ -74,6 +74,9 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+      - name: get file changes
+        run: |
+          git diff --name-only ${{ github.event.before }} ${{ github.event.after }}
 
       - name: Setup Go
         uses: actions/setup-go@v5