Skip build number commit when already up to date

The release job fails when the build number in the repo already matches
the computed value, causing git commit to exit with code 1 on an empty
changeset. Now we check for staged changes before committing.

.github/workflows/release.yml

@@ -205,8 +205,10 @@ jobs:
           git config --local user.name "github-actions[bot]"
           sed -i 's/CURRENT_PROJECT_VERSION = [0-9]*/CURRENT_PROJECT_VERSION = ${{ env.BUILD_NUMBER }}/' Yattee.xcodeproj/project.pbxproj
           git add Yattee.xcodeproj/project.pbxproj
+          git diff --cached --quiet && echo "Build number already up to date" || {
             git commit -m "Bump build number to ${{ env.BUILD_NUMBER }}"
             git push origin ${{ github.ref_name }}
+          }
       - uses: actions/download-artifact@v4
         with:
           path: artifacts