feat: ✨ add update-from-template workflow (#134)

# Description

This PR adds the `update-from-template` workflows.

Closes #108

This PR needs a quick review.

## Checklist

- [x] Added or updated tests
- [x] Updated documentation
- [] Ran `just run-all` -- will fail because it depends on the latest
version of `copier.yaml`

---------

Co-authored-by: Luke W. Johnston <[email protected]>

Author: martonvago

template/.github/workflows/update-from-template.yml

@@ -0,0 +1,55 @@
+name: Update from template
+
+on:
+  workflow_dispatch:
+  schedule:
+    # Every day at 3:30 at night.
+    - cron: '30 3 * * *'
+
+# Limit token permissions for security
+permissions: read-all
+
+jobs:
+  update-from-template:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Harden the runner (Audit all outbound calls)
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
+        with:
+          egress-policy: audit
+
+      - name: Check out repository
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
+      - name: Install Python
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        with:
+          python-version: "3.13"
+
+      - name: Install dependencies
+        run: |
+          sudo apt install pipx
+          pipx ensurepath
+          pipx install uv rust-just copier
+
+      - name: Set User
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+
+      - name: Pull request with updates from template
+        run: |
+          just update-from-template
+          any_changes=$(git status --porcelain=v1 2>/dev/null | wc -l)
+          if [ "$any_changes" -eq 0 ]; then
+            echo "No updates from the template detected, and no changes found. Stopping and exiting."
+            exit 0
+          fi
+          git checkout -b chore/update-from-template
+          git add .
+          git commit -m "chore(sync): :hammer: update changes from template"
+          gh pr create \
+            --title "chore(sync): :hammer: update changes from template" \
+            --body "This PR is automatically generated by the 'update-from-template' workflow. It syncs the latest changes from the template repository with this repository."

template/justfile.jinja

@@ -116,7 +116,8 @@ build-contributors:
 
 # Check for and apply updates from the template
 update-from-template:
-  uvx copier update --trust --defaults
+  # Do not update existing source files
+  uvx copier update --trust --defaults $(find src/{{ github_repo_snake_case }} -type f -printf "--exclude %p ")
 
 # Reset repo changes to match the template
 reset-from-template:

template/{{_copier_conf.answers_file}}.jinja

@@ -1,2 +1,2 @@
 # Changes here will be overwritten by Copier; NEVER EDIT MANUALLY
-{{ dict(_copier_answers, copyright_year=copyright_year) | to_nice_yaml -}}
+{{ dict(_copier_answers, github_repo=github_repo, copyright_year=copyright_year) | to_nice_yaml -}}