Automatically generate changelog

Fixes #1491

.github/changelog-template.md

@@ -0,0 +1,9 @@
+## [{{merge_date.strftime('%Y-%m-%d')}}]
+{%- for change_type, pulls in grouped_pulls.items() %}
+{%- if pulls %}
+### {{ change_type }}
+{%- for pull_request in pulls %}
+- {{ pull_request.title }} ([#{{ pull_request.number }}]({{ pull_request.url }}))
+{%- endfor -%}
+{% endif -%}
+{% endfor -%}

.github/workflows/update-changelog.yml

@@ -0,0 +1,34 @@
+name: Update Changelog
+
+on:
+  # Every day at 2am
+  schedule:
+    - cron: "0 2 * * *"
+  # Manual trigger
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: "3.8"
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+    - name: Update list
+      run: python scripts/update_changelog.py
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Commit changes
+      uses: stefanzweifel/git-auto-commit-action@v4
+      with:
+        commit_message: Update Changelog
+        file_pattern: CHANGELOG.md

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Change Log
 All enhancements and patches to Cookiecutter Django will be documented in this file.
 
+<!-- GENERATOR_PLACEHOLDER -->
+
 ## [2020-04-13]
 ### Changed
 - Updated to Python 3.8 (@codnee)

scripts/update_changelog.py

@@ -0,0 +1,78 @@
+import os
+from pathlib import Path
+from github import Github
+from jinja2 import Template
+import datetime as dt
+
+CURRENT_FILE = Path(__file__)
+ROOT = CURRENT_FILE.parents[1]
+GITHUB_TOKEN = os.getenv("GITHUB_TOKEN", None)
+
+# Generate changelog for PRs merged yesterday
+MERGED_DATE = dt.date.today() - dt.timedelta(days=1)
+
+
+def main() -> None:
+    """
+    Script entry point.
+    """
+    merged_pulls = list(iter_pulls())
+    if not merged_pulls:
+        print("Nothing was merged, existing.")
+        return
+
+    # Group pull requests by type of change
+    grouped_pulls = group_pulls_by_change_type(merged_pulls)
+
+    # Generate portion of markdown
+    rendered_content = generate_md(grouped_pulls)
+
+    # Update CHANGELOG.md file
+    file_path = ROOT / "CHANGELOG.md"
+    old_content = file_path.read_text()
+    updated_content = old_content.replace(
+        "<!-- GENERATOR_PLACEHOLDER -->",
+        f"<!-- GENERATOR_PLACEHOLDER -->\n\n{rendered_content}",
+    )
+    file_path.write_text(updated_content)
+
+
+def iter_pulls():
+    """Fetch merged pull requests at the date we're interested in."""
+    repo = Github(login_or_token=GITHUB_TOKEN).get_repo("pydanny/cookiecutter-django")
+    recent_pulls = repo.get_pulls(
+        state="closed", sort="updated", direction="desc"
+    ).get_page(0)
+    for pull in recent_pulls:
+        if pull.merged and pull.merged_at.date() == MERGED_DATE:
+            yield pull
+
+
+def group_pulls_by_change_type(pull_requests_list):
+    """Group pull request by change type."""
+    grouped_pulls = {
+        "Changed": [],
+        "Fixed": [],
+        "Updated": [],
+    }
+    for pull in pull_requests_list:
+        label_names = {l.name for l in pull.labels}
+        if "update" in label_names:
+            group_name = "Updated"
+        elif "bug" in label_names:
+            group_name = "Fixed"
+        else:
+            group_name = "Changed"
+        grouped_pulls[group_name].append(pull)
+    return grouped_pulls
+
+
+def generate_md(grouped_pulls):
+    """Generate markdown file from Jinja template."""
+    changelog_template = ROOT / ".github" / "changelog-template.md"
+    template = Template(changelog_template.read_text(), autoescape=True)
+    return template.render(merge_date=MERGED_DATE, grouped_pulls=grouped_pulls)
+
+
+if __name__ == "__main__":
+    main()