Add GitHub action for automated releases.

Author: HexDecimal

.github/workflows/release-on-tag.yml

@@ -0,0 +1,28 @@
+on:
+  push:
+    tags:
+      - '*.*.*'
+
+name: Create Release
+
+jobs:
+  build:
+    name: Create Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Generate body
+        run: |
+          scripts/get_release_description.py | tee release_body.md
+      - name: Create Release
+        id: create_release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ github.ref }}
+          release_name: Release ${{ github.ref }}
+          body_path: release_body.md
+          draft: true
+          prerelease: false

scripts/get_release_description.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+"""Print the description used for GitHub Releases."""
+import re
+
+TAG_BANNER = r"\d+\.\d+\.\d+\S* - \d+-\d+-\d+\n--------------------\n"
+
+RE_BODY = re.compile(fr".*?{TAG_BANNER}(.*?){TAG_BANNER}", re.DOTALL)
+RE_SECTION = re.compile(r"^(\w+)$", re.MULTILINE)
+
+
+def main() -> None:
+    # Get the most recent tag.
+    with open("CHANGELOG.rst", "r") as f:
+        match = RE_BODY.match(f.read())
+    assert match
+    body = match.groups()[0].strip()
+
+    # Add Markdown formatting to sections.
+    body = RE_SECTION.sub(r"### \1", body)
+    print(body)
+
+
+if __name__ == "__main__":
+    main()