Add scheduled workflow for cruft updates

README.md

@@ -34,6 +34,24 @@ pip install cruft
 More on cruft:
 <https://github.com/cruft/cruft>
 
+## Automatic cruft updates
+
+This template ships with a GitHub Actions workflow that will periodically (once a week) monitor changes in the template and automatically create a pull request with updates using `cruft`.
+
+### Setup
+
+The workflow requires permissions to create pull requests. You can enable it by going to Repository Settings -> Actions -> General -> Allow GitHub Actions to create and approve pull requests.
+
+### Slack notifications (optional)
+
+The bot can send notifications to a Slack channel when a new pull request with updates is created.
+
+To enable this, you need to set two secrets in your repository:
+- `SLACK_BOT_TOKEN` (the token of your Slack app)
+- `SLACK_CHANNEL_ID` (the ID of the channel where you want to receive notifications)
+
+If you don't have a Slack app, follow the [instructions here](https://github.com/slackapi/slack-github-action?tab=readme-ov-file#technique-2-slack-api-method) to create one.
+
 ## License
 
 This project is licensed under the terms of the [BSD-3 License](/LICENSE)

{{cookiecutter.repostory_name}}/.github/workflows/cruft.yml

@@ -0,0 +1,87 @@
+name: Update repository with Cruft
+permissions:
+  contents: write
+  pull-requests: write
+on:
+  schedule:
+    - cron: "0 2 * * 1" # Every Monday at 2am
+  workflow_dispatch:
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    env:
+      SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
+      SLACK_CHANNEL_ID: ${{ secrets.SLACK_CHANNEL_ID }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install Cruft
+        run: pip3 install cruft
+
+      - name: Check if update is available
+        continue-on-error: false
+        id: check
+        run: |
+          CHANGES=0
+          if [ -f .cruft.json ]; then
+            if ! cruft check; then
+              CHANGES=1
+            fi
+          else
+            echo "No .cruft.json file"
+          fi
+
+          echo "has_changes=$CHANGES" >> "$GITHUB_OUTPUT"
+
+      - name: Run update if available
+        if: steps.check.outputs.has_changes == '1'
+        run: |
+          git config --global user.email "[email protected]"
+          git config --global user.name "Cruft Updater"
+
+          cruft update --skip-apply-ask --refresh-private-variables
+          git restore --staged .
+
+      - name: Check for .rej files
+        if: steps.check.outputs.has_changes == '1'
+        id: check_rej
+        run: |
+          REJ_FILES=$(find . -name "*.rej")
+          if [ -n "$REJ_FILES" ]; then
+            echo "has_rej_files=1" >> "$GITHUB_OUTPUT"
+          else
+            echo "has_rej_files=0" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Create pull request
+        if: steps.check.outputs.has_changes == '1'
+        id: create_pr
+        uses: peter-evans/create-pull-request@v7
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          add-paths: .
+          commit-message: "Apply new Cruft update"
+          branch: cruft/update
+          delete-branch: true
+          title: Cruft cookiecutter update
+          body: |
+            This is an autogenerated PR.
+
+            ${{ steps.check_rej.outputs.has_rej_files == '1' && 'IMPORTANT: One or more `.rej` files have been detected, which means that some changes could not be applied automatically. Please RESOLVE them manually' || 'No conflicts detected' }}
+
+      - name: Post to a Slack channel
+        if: steps.create_pr.outputs.pull-request-number && env.SLACK_BOT_TOKEN
+        uses: slackapi/[email protected]
+        with:
+          method: chat.postMessage
+          token: ${{ env.SLACK_BOT_TOKEN }}
+          payload: |
+            channel: ${{ env.SLACK_CHANNEL_ID }}
+            text: |
+              <!here> cruft updates for `${{ github.repository }}`:
+              ${{ steps.create_pr.outputs.pull-request-url }}