Add upstream sync workflow (Gitea)

.github/workflows/fetch-upstream-mods.yml

@@ -0,0 +1,48 @@
+name: fetch upstream mod changes
+
+on:
+  schedule:
+    - cron: '13,43 * * * *'
+  workflow_dispatch:
+
+jobs:
+  replace-mods:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout current Gitea repo
+        uses: actions/checkout@v4
+        with:
+          lfs: true
+
+      - name: Clone upstream GitHub repo
+        run: |
+          git clone https://github.com/skyline69/balatro-mod-index.git /tmp/upstream
+
+      - name: Replace mods directory
+        run: |
+          rm -rf mods
+          cp -a /tmp/upstream/mods ./mods
+
+      - name: Install deps
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y jq moreutils
+
+      - name: Append last-updated timestamp
+        run: |
+          TIME_NOW=$(date +"%s")
+          git diff -z --name-only | grep -z meta.json | while IFS='' read -r -d '' file; do
+            jq --indent 2 '."last-updated" |= (. // '"$TIME_NOW"')' "$file" | sponge "$file"
+          done
+
+      - name: Commit and push
+        run: |
+          git config user.name "gitea-bot"
+          git config user.email "bot@smallgit.dasguney.com"
+
+          git add mods
+          if git commit -m "fetch upstream mod changes ($(date --utc +%Y%m%d_%H%M%SZ))"; then
+            git push
+          fi
+