Publish build jar to artifacts branch

.gitea/workflows/build.yml

@@ -2,11 +2,14 @@ name: Build
 
 on:
   push:
-    branches:
-      - "**"
+    branches-ignore:
+      - artifacts
   pull_request:
   workflow_dispatch:
 
+permissions:
+  contents: write
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -27,9 +30,30 @@ jobs:
       - name: Build
         run: ./gradlew build --no-daemon
 
-      - name: Upload mod jar
-        uses: actions/upload-artifact@v3
-        with:
-          name: worldhandler-1.21.1
-          path: build/libs/*.jar
-          if-no-files-found: error
+      - name: Publish jar to artifacts branch
+        if: github.event_name != 'pull_request'
+        shell: bash
+        run: |
+          set -euo pipefail
+
+          mkdir -p /tmp/worldhandler-artifacts
+          cp build/libs/*.jar /tmp/worldhandler-artifacts/
+
+          git config user.name "Gitea Actions"
+          git config user.email "actions@gitea.local"
+
+          git fetch origin artifacts || true
+          git switch --force-create artifacts
+          git rm -rf .
+
+          cp /tmp/worldhandler-artifacts/*.jar .
+          cat > README.md <<'EOF'
+          # WorldHandler build artifacts
+
+          This branch is maintained by the Gitea runner.
+          Download the jar file from this branch.
+          EOF
+
+          git add README.md *.jar
+          git commit --allow-empty -m "Publish WorldHandler jar from ${GITHUB_SHA}"
+          git push --force origin artifacts