Uniqueness is a property of HEAD alone — no base ref, no merge base, no base
blob. It sat downstream of all three, so every degradation path returned
success on a tree carrying a duplicate.
The base-blob path was the worst: a branch that introduces CHANGELOG.md hit a
bare `exit 0` on a message that was true about deletion and silent about the
duplicate in front of it. STRICT could not reach it — STRICT guards the two
skip() calls, and that is not one of them.
That inverted the two halves. Deletion needs a diff to see; duplication is the
one release-notes.sh actually mis-renders, re-arming its grab on the second
heading (#118). The half with the live extraction bug behind it had the most
ways to silently not run.
Moved, not rewritten. The skip messages now say containment skipped and that
uniqueness already passed. The CI step is no longer pull_request-only, with a
`github.ref_name` fallback because base_ref is empty on a push and a bare
`origin/` under STRICT would redden every push to main.
Found by claude-bot-andresmgsl reviewing heavy-duty/rig#99 and
heavy-duty/cast#134, which inherited the ordering from here.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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