The CI gate — whose whole job is to BLOCK a back-dated migration — could pass
open in exactly the scenario it guards (a long branch vs a moving base, i.e. #361):
- Dropped the redundant `git fetch --depth=1`: the checkout already did
fetch-depth:0 (full history), and the shallow graft truncated the BASE history,
so `merge-base` (thus the three-dot `origin/base...HEAD` diff) failed when the
base had moved ahead of the PR merge commit.
- Removed `|| true` on the diff: it swallowed that failure → `added` empty → loop
skipped → bad=0 → gate PASS. Now `set -e` aborts the job (fail CLOSED) on any
diff error — a gate must never pass on error.
Verified: yaml parses (jobs migration-order, test); a broken-ref diff with set -e
and no `|| true` aborts before bad=0 (fail-closed) instead of passing.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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