github.event.before dies with a force-push, and the merge-base fallback then
guessed a diff range: on issue/333 it reported two review-doc files while the
real diff touched custom_components/** — frontend and backend jobs silently
skipped and the run stayed success, the exact #171/#207 class of silent pass
that nearly hid a genuine backend regression from code review.
The classifier now distinguishes the two fallback cases instead of merging
them: a ZERO before is a genuinely new branch and keeps the merge-base
range; a NON-ZERO before that no longer exists is a rewritten history, and
the range is not provable — frontend/backend/integration all go true, with
a loud note in the step summary. A force-push is rare and almost always
follows a rebase, where the full run is what an honest signal costs.
The three branches of the decision are pinned by a workflow-contract unit
next to the existing performance-workflow contracts.
Issue: #347
User-Visible: no
Sergey Matyunin