Update Github release from changelog

.github/workflows/github-release.yml

@@ -0,0 +1,29 @@
+name: Prepare release
+
+on:
+  push:
+    tags:
+      - 'release-*'
+
+jobs:
+  prepare-release:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - uses: actions/setup-python@v1
+      with:
+        python-version: 3.8
+    - name: Prepare changelog
+      id: changelog
+      run: |
+        PICARD_VERSION=$(python -c "import picard; print(picard.__version__)")
+        echo "::set-output name=version::"$PICARD_VERSION
+        ./scripts/package/changelog-for-version.py $PICARD_VERSION > changes-$PICARD_VERSION.txt
+    - name: Update release
+      uses: softprops/action-gh-release@v1
+      with:
+        name: MusicBrainz Picard ${{ steps.changelog.outputs.version }}
+        body_path: changes-${{ steps.changelog.outputs.version }}.txt
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

scripts/package/changelog-for-version.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python
+
+import re
+import sys
+
+
+if len(sys.argv) == 1:
+    print("Call with changelog-for-version.py [version]", file=sys.stderr)
+    sys.exit(1)
+
+version = sys.argv[1]
+re_changes = re.compile(r'^# Version ' + re.escape(version) + '.*?\n(.*?)# Version',
+    re.DOTALL | re.MULTILINE)
+
+with open('NEWS.md', 'r') as newsfile:
+    news = newsfile.read()
+    result = re_changes.search(news)
+    if not result:
+        print("No changelog found for version %s" % version, file=sys.stderr)
+        sys.exit(1)
+    print(result[1].strip())