fix(release): collapse double blank line after Unreleased heading (#114)

Author: zfarrell

scripts/update_changelog.py

@@ -24,8 +24,8 @@ def update_changelog_text(text: str, ver: str, date: str) -> str:
                 f"- Release {ver}\n\n"
             )
         return re.sub(
-            r"^(## \[Unreleased\]\s*\n)(.*?)(?=^## \[|\Z)",
-            lambda match: match.group(1) + "\n" + section,
+            r"^## \[Unreleased\]\s*\n.*?(?=^## \[|\Z)",
+            lambda _match: f"## [Unreleased]\n\n{section}",
             text,
             count=1,
             flags=re.M | re.S,

tests/test_update_changelog.py

@@ -34,6 +34,8 @@ def test_empty_unreleased_inserts_version_without_duplicate_heading():
     assert "## [0.1.2] - 2026-05-20" in result
     assert "The format is based on [Keep a Changelog]" in result.split("## [0.1.2]")[0]
     assert result.index("## [0.1.2]") < result.index("## [0.1.1]")
+    assert "## [Unreleased]\n\n## [0.1.2]" in result
+    assert "\n\n\n" not in result
 
 
 def test_populated_unreleased_moves_notes_into_new_section():
@@ -46,3 +48,5 @@ def test_populated_unreleased_moves_notes_into_new_section():
     assert "- New widget." in result
     assert result.index("- New widget.") < result.index("## [0.1.1]")
     assert "The format is based on [Keep a Changelog]" in result.split("## [0.1.2]")[0]
+    assert "## [Unreleased]\n\n## [0.1.2]" in result
+    assert "\n\n\n" not in result