Update checkout action and push command to use dynamic branch references

.github/workflows/prettier.yml

@@ -16,6 +16,9 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v2
+        with:
+          ref: ${{ github.head_ref || github.ref_name }}
+          fetch-depth: 0
 
       - name: Set up Node.js
         uses: actions/setup-node@v2
@@ -46,4 +49,4 @@ jobs:
           git config user.email "${{ github.actor }}@users.noreply.github.com"
           git add .
           git commit -m "chore: format code with Prettier"
-          git push
+          git push origin HEAD:${{ github.head_ref || github.ref_name }}