Attempt to push with an explicit ref

.github/workflows/copyright_notice.yml

@@ -1,6 +1,8 @@
 name: Add copyright notice
 on:
   pull_request:
+permissions:
+  contents: write
 jobs:
   copyright_notice:
     runs-on: ubuntu-latest
@@ -8,6 +10,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
+          ref: ${{ github.head_ref }}
       - uses: VinnyBabuManjaly/copyright-action@v1.0.0
         with:
           CopyrightString: 'Copyright (C) 2024 Manuel Bustillo\n'
@@ -21,4 +24,4 @@ jobs:
           git add .
           git commit -m "Add copyright notice"
       - name: Push changes
-        run: git push origin HEAD:${GITHUB_REF##*/}
+        run: git push