Add documentation and tests for changelog automation

Co-authored-by: saulshanabrook <[email protected]>

Author: Copilot

.github/CHANGELOG_AUTOMATION.md

@@ -0,0 +1,36 @@
+# Automatic Changelog Generation
+
+This repository automatically generates changelog entries for new PRs using a GitHub Action.
+
+## How it works
+
+1. **Trigger**: When a PR is opened or edited
+2. **Processing**: The action runs a Python script that:
+   - Parses the `docs/changelog.md` file
+   - Finds the "## UNRELEASED" section
+   - Adds a new entry with format: `- PR_TITLE [#PR_NUMBER](PR_URL)`
+   - Checks for duplicates to avoid repeated entries
+3. **Update**: Commits the changes back to the PR branch
+
+## Files
+
+- `.github/workflows/update-changelog.yml` - GitHub Action workflow
+- `.github/scripts/update_changelog.py` - Python script that updates the changelog
+
+## Safety features
+
+- Only runs for PRs from the same repository (not forks)
+- Prevents infinite loops by excluding commits made by GitHub Action
+- Includes duplicate detection
+- Proper error handling and logging
+
+## Manual usage
+
+You can also run the script manually:
+
+```bash
+python .github/scripts/update_changelog.py \
+  --pr-number="123" \
+  --pr-title="My PR Title" \
+  --pr-url="https://github.com/egraphs-good/egglog-python/pull/123"
+```

.github/scripts/test_update_changelog.py

@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+"""
+Simple test for the changelog update script.
+"""
+
+import os
+import tempfile
+import sys
+from pathlib import Path
+
+# Add the scripts directory to the path
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', 'scripts'))
+
+from update_changelog import update_changelog, find_unreleased_section
+
+
+def test_find_unreleased_section():
+    """Test finding the unreleased section."""
+    lines = [
+        "# Changelog\n",
+        "\n",
+        "## UNRELEASED\n",
+        "\n",
+        "- Some existing entry\n",
+        "\n",
+        "## 1.0.0\n",
+        "- Released version\n"
+    ]
+    
+    unreleased_start, content_start = find_unreleased_section(lines)
+    assert unreleased_start == 2, f"Expected unreleased_start=2, got {unreleased_start}"
+    assert content_start == 4, f"Expected content_start=4, got {content_start}"
+    print("✓ find_unreleased_section test passed")
+
+
+def test_update_changelog():
+    """Test updating the changelog."""
+    # Create a temporary changelog file
+    changelog_content = """# Changelog
+
+## UNRELEASED
+
+- Existing entry
+
+## 1.0.0
+
+- Released version
+"""
+    
+    with tempfile.NamedTemporaryFile(mode='w', suffix='.md', delete=False) as f:
+        f.write(changelog_content)
+        temp_path = f.name
+    
+    try:
+        # Update the changelog
+        result = update_changelog(temp_path, "999", "Test PR", "https://example.com/pr/999")
+        assert result == True, "update_changelog should return True on success"
+        
+        # Read the updated content
+        with open(temp_path, 'r') as f:
+            updated_content = f.read()
+        
+        # Check that the entry was added
+        assert "- Test PR [#999](https://example.com/pr/999)" in updated_content
+        
+        # Check that it was added in the right place (after UNRELEASED)
+        lines = updated_content.split('\n')
+        unreleased_idx = lines.index("## UNRELEASED")
+        entry_idx = None
+        for i, line in enumerate(lines):
+            if "Test PR [#999]" in line:
+                entry_idx = i
+                break
+        
+        assert entry_idx is not None, "Entry should be found"
+        assert entry_idx > unreleased_idx, "Entry should be after UNRELEASED section"
+        
+        # Test duplicate detection
+        result2 = update_changelog(temp_path, "999", "Test PR", "https://example.com/pr/999")
+        assert result2 == False, "update_changelog should return False for duplicates"
+        
+        print("✓ update_changelog test passed")
+        
+    finally:
+        # Clean up
+        os.unlink(temp_path)
+
+
+def main():
+    """Run all tests."""
+    print("Running changelog automation tests...")
+    
+    test_find_unreleased_section()
+    test_update_changelog()
+    
+    print("✓ All tests passed!")
+
+
+if __name__ == '__main__':
+    main()

.github/workflows/update-changelog.yml

@@ -27,6 +27,9 @@ jobs:
         with:
           python-version: '3.12'
 
+      - name: Test changelog script
+        run: python .github/scripts/test_update_changelog.py
+      
       - name: Update changelog
         run: |
           python .github/scripts/update_changelog.py \