fix permissions error in build flow

Author: devalog

.github/workflows/build.yaml

@@ -6,6 +6,9 @@ on:
   pull_request:
     branches: [ main ]
 
+permissions:
+  contents: write
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -41,7 +44,11 @@ jobs:
         git config --local user.email "action@github.com"
         git config --local user.name "GitHub Action"
         git add resume.pdf
-        git diff --staged --quiet || git commit -m "Auto-update resume PDF"
-        git push
+        if git diff --staged --quiet; then
+          echo "No changes to commit"
+        else
+          git commit -m "Auto-update resume PDF"
+          git push https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/${{ github.repository }}.git HEAD:main
+        fi
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}