make pr creation conditional

.github/workflows/sync_overleaf.yml

@@ -10,13 +10,15 @@ permissions:
 name: "Sync overleaf"
 jobs:
     sync:
-        runs-on: ubuntu-latest
-        steps:
+      runs-on: ubuntu-latest
+      steps:
         - uses: actions/checkout@v4
           with:
             ref: sync_overleaf
             fetch-depth: '0'
+
         - name: Sync overleaf
+          id: sync_overleaf
           run: |
             git remote add overleaf https://git:${OVERLEAF_TOKEN}@git.overleaf.com/65df171af9ff7989580f017d
             git remote add origin_token https://git:${GITHUB_TOKEN}@github.com/columnflow/demo_docs.git
@@ -25,10 +27,14 @@ jobs:
             git pull overleaf master
             git push origin_token HEAD:sync_overleaf
 
+            commitDiffCount=$(git diff origin_token/sync_overleaf origin_token/master | wc -l)
+            echo "$foo" >> $GITHUB_OUTPUT
+
           env:
             OVERLEAF_TOKEN: ${{ secrets.OVERLEAF_TOKEN }}
             GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         - name: create pull request
+          if: steps.sync_overleaf.outputs.commitDiffCount > 0
           run: gh pr create -B master -H sync_overleaf --title 'Merge sync_overleaf into master' --body 'Created by Github action'
           env:
               GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}