Collapse the detailed changelog lists in release notes

.github/workflows/release.yml

@@ -160,8 +160,9 @@ jobs:
             echo
             echo "## Changes"
             echo
-            # The CHANGELOG section for this version, when there is one.
-            python3 scripts/changelog_section.py "${GITHUB_REF_NAME#v}" || echo "See CHANGELOG.md."
+            # The CHANGELOG section for this version, when there is one: its
+            # intro, with the detailed lists collapsed.
+            python3 scripts/changelog_section.py --collapse "${GITHUB_REF_NAME#v}" || echo "See CHANGELOG.md."
           } > notes.md
           cat notes.md
       - name: Create the GitHub release

scripts/changelog_section.py

@@ -1,11 +1,15 @@
 #!/usr/bin/env python3
 """Print the CHANGELOG.md section for one version (release-notes helper).
 
-    scripts/changelog_section.py 0.1.0-rc1
+    scripts/changelog_section.py [--collapse] 0.1.0-rc1
 
 Matches the `## [<version>]` heading and prints everything up to the next
 `## ` heading. Exits 1 when the version has no section, so the release
 workflow can fall back to a generic line.
+
+With --collapse, the section's intro (everything before its first `### `
+heading) stays visible and the rest goes in a collapsed `<details>` block, so
+a release page leads with the summary.
 """
 
 from __future__ import annotations
@@ -23,16 +27,28 @@ def section(text: str, version: str) -> str | None:
     return m.group(1).strip() if m else None
 
 
+def collapse(body: str) -> str:
+    m = re.search(r"^### ", body, re.M)
+    if m is None:
+        return body
+    intro, details = body[:m.start()].strip(), body[m.start():].strip()
+    # GitHub only renders Markdown inside <details> with blank lines around it.
+    folded = f"<details>\n<summary>Full changelog</summary>\n\n{details}\n\n</details>"
+    return f"{intro}\n\n{folded}" if intro else folded
+
+
 def main(argv: list[str]) -> int:
-    if len(argv) != 1:
+    folded = "--collapse" in argv
+    args = [a for a in argv if a != "--collapse"]
+    if len(args) != 1:
         print(__doc__, file=sys.stderr)
         return 2
     path = Path(__file__).resolve().parent.parent / "CHANGELOG.md"
-    body = section(path.read_text(encoding="utf-8"), argv[0])
+    body = section(path.read_text(encoding="utf-8"), args[0])
     if body is None:
-        print(f"no CHANGELOG section for {argv[0]}", file=sys.stderr)
+        print(f"no CHANGELOG section for {args[0]}", file=sys.stderr)
         return 1
-    print(body)
+    print(collapse(body) if folded else body)
     return 0
 
 

tests/test_changelog_section.py

@@ -0,0 +1,57 @@
+"""Release notes from CHANGELOG.md: scripts/changelog_section.py."""
+
+import importlib.util
+import unittest
+from pathlib import Path
+
+_PATH = Path(__file__).resolve().parent.parent / "scripts" / "changelog_section.py"
+_spec = importlib.util.spec_from_file_location("changelog_section", _PATH)
+changelog_section = importlib.util.module_from_spec(_spec)
+_spec.loader.exec_module(changelog_section)
+
+CHANGELOG = """# Changelog
+
+## [Unreleased]
+
+## [2.0.0] - 2026-11-01
+
+Copying replaces merging.
+
+- Works on the Steam Frame
+
+### Added
+
+- A thing
+
+### Fixed
+
+- Another thing
+
+## [1.0.0] - 2026-09-21
+
+### Added
+
+- First release
+"""
+
+
+class CollapseTests(unittest.TestCase):
+    def test_keeps_the_intro_and_folds_the_lists(self):
+        body = changelog_section.section(CHANGELOG, "2.0.0")
+        self.assertEqual(changelog_section.collapse(body), (
+            "Copying replaces merging.\n\n- Works on the Steam Frame\n\n"
+            "<details>\n<summary>Full changelog</summary>\n\n"
+            "### Added\n\n- A thing\n\n### Fixed\n\n- Another thing\n\n</details>"))
+
+    def test_a_section_without_an_intro_is_all_folded(self):
+        body = changelog_section.section(CHANGELOG, "1.0.0")
+        self.assertEqual(changelog_section.collapse(body), (
+            "<details>\n<summary>Full changelog</summary>\n\n"
+            "### Added\n\n- First release\n\n</details>"))
+
+    def test_a_section_without_subheadings_is_unchanged(self):
+        self.assertEqual(changelog_section.collapse("Just a note."), "Just a note.")
+
+
+if __name__ == "__main__":
+    unittest.main()