ci: count migration-gate tests via nextest JSON, not human-format indentation
The count-floor guard (#4673) parsed nextest's human list format with
grep -c '^ '. CI's newer nextest emits a different indentation, so the
count collapsed to 0 and the gate failed on every PR based on current
main (first observed on #4683, then #4674/#4677/#4680). Count via
--message-format json + jq instead, which is stable across versions, and
fail loudly if the JSON shape ever changes.
The migration-proof step in ci.yml selects tests by name substring
(data_movement / rebalance / decommission / source_cleanup /
delete_marker), so a rename can silently thin the gate to zero with no
CI signal. Move the filter expression into
scripts/check_migration_gate_count.sh as its single source of truth:
the script counts the selected tests with cargo nextest list, fails if
the count drops below the committed floor in
.config/migration-gate-floor.txt, and then runs the gate with the same
filter so the check and the run cannot drift.
The floor equals the exact selected-test count at landing (571), so any
reduction fails CI and intentional shrinks must edit the floor file in
the same PR, keeping gate changes visible in diffs.
Refs rustfs/backlog#1153 (infra-12), rustfs/backlog#1155.
Signed-off-by: Zhengchao An <anzhengchao@gmail.com>
Zhengchao An