Add update_changelog script and integrate it into release workflow

.github/workflows/release.yml

@@ -43,6 +43,10 @@ jobs:
           NEW_VERSION=$(python -c "import version; print(f'{version.__version__}')")
           echo "new_version=${NEW_VERSION}" >> $GITHUB_OUTPUT
 
+      - name: Update Changelog
+        run: |
+          python scripts/update_changelog.py ${{ steps.update_version.outputs.new_version }}
+
       - name: Set repository metadata
         id: meta
         run: |
@@ -54,7 +58,7 @@ jobs:
 
       - name: Commit and Tag
         run: |
-          git add version.py
+          git add version.py CHANGELOG.md
           git commit -m "Release v${{ steps.update_version.outputs.new_version }}"
           git tag -a "v${{ steps.update_version.outputs.new_version }}" -m "Release v${{ steps.update_version.outputs.new_version }}"
           git push origin main --tags

scripts/update_changelog.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python
+"""
+Updates the CHANGELOG.md file for a new release.
+Renames [Unreleased] section to the new version with current date.
+Usage: python update_changelog.py <version>
+"""
+import re
+import sys
+from datetime import datetime
+from pathlib import Path
+
+
+def update_changelog(version):
+    """Update CHANGELOG.md with new version and date."""
+    changelog_file = Path(__file__).parent.parent / "CHANGELOG.md"
+    
+    if not changelog_file.exists():
+        print("CHANGELOG.md not found")
+        sys.exit(1)
+    
+    content = changelog_file.read_text(encoding='utf-8')
+    
+    # Check if there's an Unreleased section
+    if '## [Unreleased]' not in content:
+        print("No [Unreleased] section found in CHANGELOG.md")
+        sys.exit(1)
+    
+    # Get current date in YYYY-MM-DD format
+    today = datetime.now().strftime('%Y-%m-%d')
+    
+    # Replace [Unreleased] with new version and date, and add new [Unreleased] section
+    # This pattern preserves everything after [Unreleased] until the next version or end
+    new_content = re.sub(
+        r'## \[Unreleased\]',
+        f'## [Unreleased]\n\n## [{version}] - {today}',
+        content,
+        count=1
+    )
+    
+    if new_content == content:
+        print("Failed to update CHANGELOG.md")
+        sys.exit(1)
+    
+    changelog_file.write_text(new_content, encoding='utf-8')
+    print(f"CHANGELOG.md updated for version {version} ({today})")
+    return True
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage: python update_changelog.py <version>")
+        print("Example: python update_changelog.py 0.13.0")
+        sys.exit(1)
+    
+    version = sys.argv[1]
+    # Remove 'v' prefix if present
+    version = version.lstrip('v')
+    
+    update_changelog(version)