feat: implement optimization #9 - release notes from CHANGELOG

Add release notes extraction from CHANGELOG for publishing:

- Create ChangelogParser class to extract version sections from CHANGELOG
- Support multiple output formats: markdown, plain text, HTML
- Add 'release notes VERSION' CLI command to extract notes
- Auto-detect latest version if not specified
- Support piping to gh/gitea release commands
- Save to file with --output option
- Plain text format removes markdown formatting
- HTML format converts markdown to HTML

This streamlines creating release notes for GitHub/Gitea releases
by extracting CHANGELOG content automatically.

Usage:
  release notes 0.10.0                    # Extract markdown notes
  release notes                           # Latest version
  release notes 0.10.0 --format plain    # Plain text
  release notes 0.10.0 -o notes.md       # Save to file
  release notes 0.10.0 | gh release create v0.10.0 -F -

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

capabilities/release-management/src/release_management/changelog/__init__.py

@@ -5,5 +5,6 @@ This package provides tools for working with CHANGELOG.md files.
 """
 
 from .editor import ChangelogEditor
+from .parser import ChangelogParser
 
-__all__ = ['ChangelogEditor']
+__all__ = ['ChangelogEditor', 'ChangelogParser']

capabilities/release-management/src/release_management/changelog/parser.py

@@ -0,0 +1,179 @@
+"""
+CHANGELOG.md parser for extracting release notes.
+
+This module provides tools for parsing CHANGELOG.md files and extracting
+version-specific content for release notes.
+"""
+
+import re
+from pathlib import Path
+from typing import Optional
+
+
+class ChangelogParser:
+    """Parse CHANGELOG.md files and extract release information."""
+
+    def __init__(self, changelog_path: Optional[Path] = None):
+        """Initialize changelog parser.
+
+        Args:
+            changelog_path: Path to CHANGELOG.md file
+        """
+        self.changelog_path = changelog_path or Path.cwd() / 'CHANGELOG.md'
+
+    def extract_version_section(self, version: str, format: str = 'markdown') -> str:
+        """Extract CHANGELOG section for a specific version.
+
+        Args:
+            version: Version to extract (e.g., "0.10.0")
+            format: Output format ('markdown', 'plain', 'html')
+
+        Returns:
+            Formatted content of the version section
+        """
+        if not self.changelog_path.exists():
+            return f"Error: CHANGELOG.md not found at {self.changelog_path}"
+
+        try:
+            version_clean = version.lstrip('v')
+
+            with open(self.changelog_path) as f:
+                content = f.read()
+
+            # Find the version section using regex
+            # Match: ## [VERSION] - DATE followed by content until next ## [
+            pattern = rf"## \[{re.escape(version_clean)}\].*?\n\n(.*?)(?=\n## \[|\Z)"
+            match = re.search(pattern, content, re.DOTALL)
+
+            if not match:
+                return f"Error: No section found for version {version_clean} in CHANGELOG.md"
+
+            section_content = match.group(1).strip()
+
+            if not section_content:
+                return f"Warning: Section for version {version_clean} exists but is empty"
+
+            # Format based on requested format
+            if format == 'plain':
+                return self._to_plain(section_content)
+            elif format == 'html':
+                return self._to_html(section_content)
+            else:
+                return section_content  # markdown (default)
+
+        except Exception as e:
+            return f"Error reading CHANGELOG: {e}"
+
+    def get_latest_version(self) -> Optional[str]:
+        """Get the latest version number from CHANGELOG.
+
+        Returns:
+            Latest version string or None if not found
+        """
+        if not self.changelog_path.exists():
+            return None
+
+        try:
+            with open(self.changelog_path) as f:
+                content = f.read()
+
+            # Find first version section (skip Unreleased)
+            pattern = r"## \[(\d+\.\d+\.\d+[^\]]*)\]"
+            match = re.search(pattern, content)
+
+            return match.group(1) if match else None
+
+        except Exception:
+            return None
+
+    def list_versions(self) -> list:
+        """List all versions in CHANGELOG.
+
+        Returns:
+            List of version strings
+        """
+        if not self.changelog_path.exists():
+            return []
+
+        try:
+            with open(self.changelog_path) as f:
+                content = f.read()
+
+            # Find all version sections (excluding Unreleased)
+            pattern = r"## \[(\d+\.\d+\.\d+[^\]]*)\]"
+            matches = re.findall(pattern, content)
+
+            return matches
+
+        except Exception:
+            return []
+
+    def _to_plain(self, markdown_content: str) -> str:
+        """Convert markdown content to plain text.
+
+        Args:
+            markdown_content: Markdown formatted content
+
+        Returns:
+            Plain text content
+        """
+        # Remove markdown formatting
+        plain = markdown_content
+
+        # Remove bold/italic
+        plain = re.sub(r'\*\*([^*]+)\*\*', r'\1', plain)  # bold
+        plain = re.sub(r'\*([^*]+)\*', r'\1', plain)  # italic
+        plain = re.sub(r'__([^_]+)__', r'\1', plain)  # bold (underscores)
+        plain = re.sub(r'_([^_]+)_', r'\1', plain)  # italic (underscores)
+
+        # Remove links but keep text
+        plain = re.sub(r'\[([^\]]+)\]\([^\)]+\)', r'\1', plain)
+
+        # Remove inline code backticks
+        plain = re.sub(r'`([^`]+)`', r'\1', plain)
+
+        # Convert headers to plain text with spacing
+        plain = re.sub(r'^### (.+)$', r'\n\1:', plain, flags=re.MULTILINE)
+        plain = re.sub(r'^## (.+)$', r'\n\1\n' + '=' * 40, plain, flags=re.MULTILINE)
+
+        return plain.strip()
+
+    def _to_html(self, markdown_content: str) -> str:
+        """Convert markdown content to HTML.
+
+        Args:
+            markdown_content: Markdown formatted content
+
+        Returns:
+            HTML formatted content
+        """
+        try:
+            import markdown
+            return markdown.markdown(markdown_content)
+        except ImportError:
+            # Fallback to basic HTML conversion if markdown package not available
+            html = markdown_content
+
+            # Headers
+            html = re.sub(r'^### (.+)$', r'<h3>\1</h3>', html, flags=re.MULTILINE)
+            html = re.sub(r'^## (.+)$', r'<h2>\1</h2>', html, flags=re.MULTILINE)
+
+            # Bold/italic
+            html = re.sub(r'\*\*([^*]+)\*\*', r'<strong>\1</strong>', html)
+            html = re.sub(r'\*([^*]+)\*', r'<em>\1</em>', html)
+
+            # Links
+            html = re.sub(r'\[([^\]]+)\]\(([^\)]+)\)', r'<a href="\2">\1</a>', html)
+
+            # Code
+            html = re.sub(r'`([^`]+)`', r'<code>\1</code>', html)
+
+            # Lists
+            html = re.sub(r'^- (.+)$', r'<li>\1</li>', html, flags=re.MULTILINE)
+            html = re.sub(r'(<li>.*</li>)', r'<ul>\1</ul>', html, flags=re.DOTALL)
+
+            # Paragraphs
+            html = re.sub(r'\n\n', '</p><p>', html)
+            html = f'<p>{html}</p>'
+
+            return html

capabilities/release-management/src/release_management/cli/main.py

@@ -12,6 +12,7 @@ from typing import Optional
 from ..core.manager import ReleaseManager
 from ..utils.version import VersionManager
 from ..changelog.editor import ChangelogEditor
+from ..changelog.parser import ChangelogParser
 from ..summary.generator import SummaryGenerator
 
 
@@ -358,5 +359,58 @@ def summary(ctx, version: str, output: Optional[Path]):
         sys.exit(1)
 
 
+@main.command('notes')
+@click.argument('version', required=False)
+@click.option('--format', 'output_format', type=click.Choice(['markdown', 'plain', 'html']),
+              default='markdown', help='Output format (default: markdown)')
+@click.option('--output', '-o', default=None, type=click.Path(path_type=Path),
+              help='Save to file instead of stdout')
+@click.pass_context
+def notes(ctx, version: Optional[str], output_format: str, output: Optional[Path]):
+    """Extract release notes from CHANGELOG.md.
+
+    Extracts the CHANGELOG section for a specific version and outputs it
+    in various formats. Useful for creating GitHub/Gitea release notes.
+
+    If no version is specified, uses the latest version from CHANGELOG.
+
+    Examples:
+        release notes 0.10.0              # Extract v0.10.0 notes (markdown)
+        release notes                     # Extract latest version notes
+        release notes 0.10.0 --format plain  # Plain text format
+        release notes 0.10.0 -o notes.md     # Save to file
+        release notes 0.10.0 | gh release create v0.10.0 -F -  # Pipe to gh
+    """
+    project_root = ctx.obj['project_root'] or Path.cwd()
+    changelog_path = project_root / 'CHANGELOG.md'
+
+    parser = ChangelogParser(changelog_path)
+
+    # Get version (use latest if not specified)
+    if version is None:
+        version = parser.get_latest_version()
+        if version is None:
+            print("❌ Could not determine version from CHANGELOG.md")
+            sys.exit(1)
+        print(f"Using latest version: {version}", file=sys.stderr)
+
+    # Extract content
+    content = parser.extract_version_section(version, format=output_format)
+
+    # Check for errors
+    if content.startswith("Error:") or content.startswith("Warning:"):
+        print(content)
+        sys.exit(1 if content.startswith("Error:") else 0)
+
+    # Output
+    if output:
+        if not output.is_absolute():
+            output = project_root / output
+        output.write_text(content)
+        print(f"✅ Release notes written to {output}", file=sys.stderr)
+    else:
+        print(content)
+
+
 if __name__ == '__main__':
     main()