ci: centralize path-gating behind single orchestrator + all-checks-pass
gate
Replace the scattered per-workflow detect-changes pattern with a single
ci.yml orchestrator that runs the classifier once, then conditionally
calls sub-workflows via workflow_call based on lane outputs. A final
all-checks-pass job (if: always()) aggregates all results so branch
protection only needs to require one check.
Changes:
- New .github/workflows/ci.yml orchestrator (detect + conditional calls
+ all-checks-pass gate)
- Extend classify_changes.py with scan/deps/mcp_catalog lanes, absorbing
supply-chain-audit's internal changes job
- Update detect-changes/action.yml to expose the new lane outputs
- Convert all 10 PR-gated sub-workflows to workflow_call-only triggers,
removing their push/pull_request triggers and per-step detect-changes
guards (gating now happens at the orchestrator level)
- lint.yml + supply-chain-audit.yml receive event_name as a
workflow_call
input to replace github.event_name (which is "workflow_call" inside
called workflows)
- supply-chain-audit.yml: remove internal changes job + *-gate jobs
(orchestrator handles gating, booleans arrive as inputs)
- contributor-check.yml: remove internal filter step
- Update test_classify_changes.py for 6-lane output + new supply-chain
test cases
Catches the failure mode that produced #25045: a contributor PR whose
branch had been disconnected from main's history (likely an accidental
'git checkout --orphan' or '.git/' re-init). GitHub's merge UI does
not refuse merges of unrelated histories, so the PR landed cleanly
with its intended one-file change but its parent-less root commit
(413990c94) got grafted into main as a second root. The merge
resolution itself was correct — main's content won for every
conflicting file — but ~1500 files' worth of git blame collapsed
onto that single commit.
Implementation: 'git merge-base origin/main HEAD' exits non-zero and
prints nothing when the two commits share no ancestor. Check both
conditions and fail with a clear message + recovery steps.
Verified: against the historic state of PR #25045 (base 5d90386ba,
head 1149e75db), 'git merge-base' returns empty with exit 1, so the
new check would have rejected it.
