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fix(FN-5090): use live merge-base in classifyForeignOnlyContamination

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When task.baseCommitSha becomes stale (because main has advanced past
it via legitimate merges of OTHER tasks), git log baseSha..branchName
includes commits that are already on main with foreign task-id
attribution. classifyForeignOnlyContamination then returns
kind="ambiguous" — own commits AND foreign commits in range — and the
contamination recovery skips, blocking the merger handoff
indefinitely.

This stranded FN-5092 after manual merges of FN-5060/FN-5090/FN-5053
moved main forward without updating downstream tasks' baseCommitSha.

Fix: when git merge-base(branch, main) is a descendant of the
persisted baseSha, prefer the live merge-base for the contamination
classification range. Fail open to persisted baseSha on any git
error. Also pass the effective base to classifyBootstrapMisbinding
so both classifiers see consistent input.

Fusion-Task-Id: FN-5090
This commit is contained in:
gsxdsm
2026-05-18 21:23:19 -07:00
parent b9d4bd8c1b
commit fac81b8432
1 changed files with 23 additions and 2 deletions
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25
packages/engine/src/branch-conflicts.ts
View File

@@ -592,7 +592,28 @@ export async function classifyForeignOnlyContamination(
input: ClassifyForeignOnlyContaminationInput,
): Promise<ClassifyForeignOnlyContaminationResult> {
const { repoDir, branchName, baseSha, taskId, mainRef = "main" } = input;
const output = await runGit(repoDir, `git log --format=%H%x1f%s%x1f%b ${quoteShellArg(`${baseSha}..${branchName}`)}`)
// FN-5090 hotfix: stale baseSha (older than the actual fork point with main) caused
// classifyForeignOnlyContamination to see commits that have since been merged into main
// as "foreign", returning kind:"ambiguous" and stranding the task. Prefer the live
// merge-base when it is a descendant of the persisted baseSha.
let effectiveBaseSha = baseSha;
try {
const mergeBaseRaw = await runGit(repoDir, `git merge-base ${quoteShellArg(branchName)} ${quoteShellArg(mainRef)}`);
const liveMergeBase = mergeBaseRaw.trim();
if (liveMergeBase && liveMergeBase !== baseSha) {
// Use live merge-base if it is a descendant of baseSha (newer)
const ancestryCheck = await runGit(
repoDir,
`git merge-base --is-ancestor ${quoteShellArg(baseSha)} ${quoteShellArg(liveMergeBase)} && echo yes || echo no`,
).catch(() => "no");
if (ancestryCheck.trim() === "yes") {
effectiveBaseSha = liveMergeBase;
}
}
} catch {
// fall back to persisted baseSha on any git failure
}
const output = await runGit(repoDir, `git log --format=%H%x1f%s%x1f%b ${quoteShellArg(`${effectiveBaseSha}..${branchName}`)}`)
.catch(() => "");
const subjectPattern = /^(feat|fix|test|chore|docs|refactor|perf|build)\((FN-\d+)\):/i;
const trailerPattern = /(?:^|\n)Fusion-Task-Id:\s*(FN-\d+)\s*(?:\n|$)/i;
@@ -610,7 +631,7 @@ export async function classifyForeignOnlyContamination(
const bootstrap = await classifyBootstrapMisbinding({
repoDir,
branchName,
baseSha,
baseSha: effectiveBaseSha,
taskId,
foreignCommits,
});