Review found the first cut incomplete, and the gap is the shape the #118
incident actually had. Containment catches a heading that VANISHED. It cannot
catch one that was DUPLICATED: the duplicate is head-side surplus, and
`comm -23` (base minus head) is blind to extras on the head side -- with or
without `sort -u`. Multiset comparison does not close it either, for the same
reason: base {0.8.0} minus head {0.8.0, 0.8.0} is still empty. The assert that
does close it is uniqueness of version headings ON HEAD, kept ALONGSIDE
containment rather than replacing it, since containment remains the right
check for deletions.
That matters because the duplicate is not hypothetical. It is what a bad
rebase of #116 produced an hour before this commit: two
`## 0.8.0 - 2026-07-19` headings with the incoming entry stranded between
them. Every other guard was green on that tree -- no conflict markers,
changelog-armed.sh happy because the top section was still right for the
VERSION, tests and shellcheck clean -- while release-notes.sh re-armed its
grab on the second heading and folded post-cut prose into the shipped 0.8.0
body, and the stranded entry would have been dropped from the next release's
notes as well.
Uniqueness fires on nothing legitimate: the ceremony stamps a NEW version, and
'Unreleased' fails the version shape before it reaches here.
Both trees are now pinned in test/release.sh side by side -- the deletion
near-miss and the real duplicate -- each with changelog-armed.sh asserted
green on it, which is the whole reason this script exists separately. The
duplicate case also pins that the containment arm stays silent on it, so a
future simplification cannot collapse the two asserts into one.
Proven non-vacuous: stubbing the uniqueness check to empty turns the suite red
on exactly the three new assertions (117/3); restoring it returns 120/0.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
changelog-armed.sh asks only whether the TOP section agrees with VERSION.
A PR that replaces '## X.Y.Z — DATE' with its own '## Unreleased' block —
git merges the edit cleanly, and a shipped section is silently absorbed into
Unreleased. The damage only surfaces at the next release, when
release-notes.sh cannot find the section it extracts by heading.
Add changelog-monotonic.sh: the set of '^## X.Y.Z' headings on a branch must
be a superset of the set at the merge base. Release headings are append-only,
so the rule has no legitimate violation — and the ceremony's stamp passes by
construction, adding X.Y.Z and removing none.
Its own script, not a clause in changelog-armed.sh: the input is a git
history rather than two files, no base ref is a SKIP rather than a failure,
and changelog-armed.sh is driven by test/release.sh against constructed
non-git trees that cannot express the failure at all.
CI checks out with fetch-depth: 0 and sets CHANGELOG_MONOTONIC_STRICT=1, so
an unreachable base ref goes red there instead of degrading to the skip a
local run is allowed.
Closes#122
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
