Do not fail Vendor.yml when no changes imported

This change improves the check in the DuckDB engine sources vendoring
process. If no changes are detected in the incoming sources then the
remaining of the `Vendor.yml` job is skipped instead of moving it to
"Failure" state.

Testing: debugged this in a separate repo.

Author: staticlibs

.github/workflows/Vendor.yml

@@ -63,31 +63,37 @@ jobs:
           git checkout vendoring-${{ github.ref_name }}
           git rebase ${{ github.ref_name }}
           # Call the vendoring script in the engine
-          git rm -rf src/duckdb
+          rm -rf src/duckdb
           python vendor.py --duckdb .git/duckdb
-          git add src/duckdb CMakeLists.txt
           # Clean up
           rm -rf .git/duckdb
           # Export vendor revision for use in later steps
           echo "vendor_rev=${REV}" >> "${GITHUB_OUTPUT}"
 
+      - name: Check for incoming changes
+        if: ${{ steps.vendor.outcome == 'success' }}
+        id: check_for_changes
+        run: |
+          if git diff --exit-code; then
+            echo "No vendoring changes detected, skipping the remaining of the job."
+          else
+            echo "Changes detected, proceeding with commit and push."
+            echo "has_changes=true" >> "${GITHUB_OUTPUT}"
+          fi
+
       - name: Commit and push the changes
         id: commit_and_push
+        if: ${{ steps.check_for_changes.outcome == 'success' && steps.check_for_changes.outputs.has_changes == 'true' }}
         run: |
           MSG="Update vendored DuckDB sources to ${{ steps.vendor.outputs.vendor_rev }}"
+          git add src/duckdb CMakeLists.txt
           git commit -m "${MSG}"
-          # Check if ahead of upstream branch
-          # If yes, set a step output
-          git push -f --dry-run origin vendoring-${{ github.ref_name }}
-          if [ $(git rev-list HEAD...origin/${{ github.ref_name }} --count) -gt 0 ]; then
-            git push -f origin vendoring-${{ github.ref_name }}
-            # Avoid set-output, it's deprecated
-            echo "push_performed=true" >> "${GITHUB_OUTPUT}"
-            echo "commit_msg=${MSG}" >> "${GITHUB_OUTPUT}"
-          fi
+          git push -f origin vendoring-${{ github.ref_name }}
+          echo "commit_msg=${MSG}" >> "${GITHUB_OUTPUT}"
 
       - name: Check PR exists
         id: check_pr_exists
+        if: ${{ steps.commit_and_push.outcome == 'success' }}
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
@@ -103,6 +109,7 @@ jobs:
 
       - name: Prepare PR message
         id: prepare_pr_message
+        if: ${{ steps.check_pr_exists.outcome == 'success' }}
         run: |
             DATE="$(date +"%Y-%m-%d %H:%M:%S")"
             CHANGE_LABEL="duckdb/duckdb#${{ steps.vendor.outputs.vendor_rev }}"
@@ -113,7 +120,7 @@ jobs:
 
       - name: Create PR
         id: create_pr
-        if: ${{ steps.check_pr_exists.outputs.pr_exists == 'false' }}
+        if: ${{ steps.prepare_pr_message.outcome == 'success' && steps.check_pr_exists.outputs.pr_exists == 'false' }}
         env:
           # We cannot use default workflow's GITHUB_TOKEN here, because
           # it is restricted to not trigger 'pull_request' event that
@@ -133,7 +140,7 @@ jobs:
 
       - name: Update PR
         id: update_pr
-        if: ${{ steps.check_pr_exists.outputs.pr_exists == 'true' }}
+        if: ${{ steps.prepare_pr_message.outcome == 'success' && steps.check_pr_exists.outputs.pr_exists == 'true' }}
         env:
           # We cannot use default workflow's GITHUB_TOKEN here, because
           # it is restricted to not trigger 'pull_request' event that