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fix(engine): skip promoted-foreign commits in contamination audit

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assertCleanBranchAtBase now checks each foreign-attributed commit
against `git merge-base --is-ancestor <sha> main`. If the commit is
already on local main, it was promoted through integration regardless
of whose Fusion-Task-Id trailer it carries — treating it as foreign
contamination is wrong and was the root cause of the FN-5475 cascade
(downstream worktrees inherited a sibling task's tip during the brief
fast-forward window before main moved further).

Audit cost: O(N) extra git calls per audit run, where N is the number
of foreign-trailer commits in baseSha..branchName. Each call is ~5-10ms
and N is typically 1-5. Negligible relative to the surrounding I/O.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
gsxdsm
2026-05-23 02:59:23 -07:00
parent a7ad30f22a
commit 02971efcfe
3 changed files with 104 additions and 2 deletions
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42
packages/engine/src/__tests__/branch-conflicts.test.ts
View File

@@ -466,6 +466,48 @@ describe("branch-conflicts", () => {
await expect(assertion).resolves.toBeUndefined();
});
// FN-5475 / option-2 promotion check: a commit attributed to another
// task that's already reachable from local `main` was integrated via
// fast-forward and shouldn't be treated as contamination on a
// downstream branch that briefly inherited it.
it("assertCleanBranchAtBase treats foreign-attributed commits that are ancestors of main as promoted", async () => {
mockedExecSync.mockImplementation((cmd: string | string[]) => {
const command = typeof cmd === "string" ? cmd : cmd[0];
if (command.includes("git log --format=%H%x1f%s%x1f%b 'main..fusion/fn-4068'")) {
return Buffer.from("bbb222feat(FN-4386): foreignFusion-Task-Id: FN-4386\n");
}
if (command.includes("git merge-base --is-ancestor 'bbb222' 'main'")) {
// Simulate the FN-5475 case: foreign commit is already on main.
return Buffer.from("");
}
throw new Error(`Unexpected command: ${command}`);
});
await expect(
assertCleanBranchAtBase("/tmp/repo", "fusion/fn-4068", "main", "FN-4068"),
).resolves.toBeUndefined();
});
it("assertCleanBranchAtBase still throws when foreign-attributed commits are NOT on main", async () => {
mockedExecSync.mockImplementation((cmd: string | string[]) => {
const command = typeof cmd === "string" ? cmd : cmd[0];
if (command.includes("git log --format=%H%x1f%s%x1f%b 'main..fusion/fn-4068'")) {
return Buffer.from("bbb222feat(FN-4386): foreignFusion-Task-Id: FN-4386\n");
}
if (command.includes("git merge-base --is-ancestor")) {
// Not on main — exits non-zero.
const err = new Error("not an ancestor") as Error & { stderr?: string };
err.stderr = "";
throw err;
}
throw new Error(`Unexpected command: ${command}`);
});
await expect(
assertCleanBranchAtBase("/tmp/repo", "fusion/fn-4068", "main", "FN-4068"),
).rejects.toBeInstanceOf(BranchCrossContaminationError);
});
describe("reportBranchAttribution", () => {
const RS = "\x1e";
const FS = "\x1f";