Add auto-update workflow

.gitea/workflows/auto-update.yaml

@@ -0,0 +1,39 @@
+# Based on https://github.com/infinilabs/gitea-pr/blob/main/action.yml
+
+name: Auto update flake.lock
+
+on:
+  workflow_dispatch: # allows manual triggering
+  schedule:
+    - cron: "0 0 * * 0" # runs weekly on Sunday at 00:00
+
+jobs:
+  auto-update:
+    runs-on: basic-nix
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v4
+
+      - name: Login to Gitea
+        shell: bash
+        env:
+          GIT_SERVER_URL: tea.notadev.net
+          GIT_SERVER_TOKEN: ${{ secrets.token }}
+        run: >-
+          cd "${{ env.GITHUB_WORKSPACE }}" &&
+          echo "$PWD" &&
+          export XDG_CONFIG_HOME="$PWD" &&
+          tea login add
+          -u "$GIT_SERVER_URL"
+          -t "$GIT_SERVER_TOKEN"
+
+      - name: Update flake.lock
+        run: nix flake update
+
+      - name: Create PR
+        shell: bash
+        run: >-
+          cd "${{ env.GITHUB_WORKSPACE }}" &&
+          echo "$PWD" &&
+          export XDG_CONFIG_HOME="$PWD" &&
+          tea pr create --head "update-lockfile" --base "main" --title "Update flake.lock"