update_changelog used to blindly prepend the new ## [version] entry to
the entire file body. When CHANGELOG.md leads with a # Changelog H1
the result was:
## [new] - YYYY-MM-DD
...
# Changelog
## [old] - ...
which trips markdownlint MD041 (first-line-h1) and MD012
(no-multiple-blanks), and reads as if the document were two stacked
changelogs.
The new _insert_after_h1 helper:
* Synthesises # Changelog when the file is empty.
* Inserts the entry between the existing H1 (plus any intro prose)
and the first existing ## release entry.
* For legacy headerless files (file starts with ##) prepends the
synthesised H1 + entry, so the resulting document is also
MD041-clean.
Tests cover the three layouts (empty, H1+existing-entries,
legacy-headerless). All 61 release-unit tests stay green.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Kevin Veen-Birkenbach
ece575cc73