Prefer the syncing version's own release as scan base

src/base-sha.test.ts

@@ -18,10 +18,11 @@ function commit(cwd: string, file: string, content: string, message: string): st
   return runGit("rev-parse HEAD", cwd);
 }
 
-function release(name: string, commitSha: string | undefined, daysAgoCreated: number): Release {
+function release(name: string, commitSha: string | undefined, daysAgoCreated: number, version?: string): Release {
   return {
     id: `id-${name}`,
     name,
+    version,
     commitSha,
     createdAt: new Date(Date.now() - daysAgoCreated * 24 * 60 * 60 * 1000).toISOString(),
   };
@@ -61,11 +62,11 @@ function buildRepo() {
 
   // Back to main
   runGit("checkout -q main", cwd);
-  commit(cwd, "f", "2", "m2");
+  const m2 = commit(cwd, "f", "2", "m2");
   const mainPrev = commit(cwd, "f", "3", "m3 (1.71.0 release)");
   const mainHead = commit(cwd, "f", "4", "m4 (1.72.0 HEAD)");
 
-  return { cwd, hotfixSha, hotfixHead, mainPrev, mainHead };
+  return { cwd, m1, m2, hotfixSha, hotfixHead, mainPrev, mainHead };
 }
 
 describe("findBaseSha", () => {
@@ -127,6 +128,40 @@ describe("findBaseSha", () => {
   it("scenario F — empty list (first-ever sync): returns fallback", () => {
     expect(findBaseSha([], repo.mainHead, deps)).toEqual({ kind: "fallback" });
   });
+
+  it("scenario G — zombie ordering without a version match: picks the stale reachable candidate", () => {
+    // Server-side recency ordering is the guard against stale started releases
+    // appearing first; without a version match, the existing walk is preserved.
+    const candidates = [
+      release("stale started release", repo.m1, 21),
+      release("newer completed release", repo.mainPrev, 1),
+    ];
+    expect(findBaseSha(candidates, repo.mainHead, deps)).toEqual({ kind: "found", sha: repo.m1 });
+  });
+
+  it("scenario H — reachable version match: takes priority over an earlier reachable candidate", () => {
+    const candidates = [
+      release("stale started release", repo.m1, 21),
+      release("newer completed release", repo.mainPrev, 1),
+      release("matching release", repo.m2, 2, "1.72.0"),
+    ];
+    expect(findBaseSha(candidates, repo.mainHead, deps, "1.72.0")).toEqual({
+      kind: "found",
+      sha: repo.m2,
+    });
+  });
+
+  it("scenario I — non-ancestor version match: falls back to the normal walk", () => {
+    const candidates = [
+      release("stale started release", repo.m1, 21),
+      release("unreachable matching release", repo.hotfixSha, 2, "1.72.0"),
+      release("newer completed release", repo.mainPrev, 1),
+    ];
+    expect(findBaseSha(candidates, repo.mainHead, deps, "1.72.0")).toEqual({
+      kind: "found",
+      sha: repo.m1,
+    });
+  });
 });
 
 /**

src/base-sha.ts

@@ -12,8 +12,27 @@ export type FindBaseShaDeps = {
  * release candidates (most-relevant first). Returns the first candidate whose
  * `commitSha` is reachable from `headSha` — the API can't disambiguate
  * concurrent release trains via SQL alone, so we use git as ground truth.
+ * When a syncing version is supplied, a reachable candidate with that version
+ * takes priority over the list order.
  */
-export function findBaseSha(candidates: Release[], headSha: string, deps: FindBaseShaDeps): BaseShaResult {
+export function findBaseSha(
+  candidates: Release[],
+  headSha: string,
+  deps: FindBaseShaDeps,
+  syncingVersion?: string,
+): BaseShaResult {
+  if (syncingVersion !== undefined) {
+    for (const candidate of candidates) {
+      if (candidate.version !== syncingVersion || !candidate.commitSha) {
+        continue;
+      }
+      if (deps.verifyAncestorReachable(candidate.commitSha, headSha)) {
+        verbose(`Using base SHA from release "${candidate.name}" (${candidate.commitSha.slice(0, 7)})`);
+        return { kind: "found", sha: candidate.commitSha };
+      }
+    }
+  }
+
   for (const candidate of candidates) {
     const sha = candidate.commitSha;
     if (!sha) {

src/index.ts

@@ -292,7 +292,7 @@ async function syncCommand(): Promise<{
   }
 
   const recentReleases = await getRecentReleases();
-  const scanBase = getScanBase(recentReleases, currentCommit.commit);
+  const scanBase = getScanBase(recentReleases, currentCommit.commit, releaseVersion);
   let latestSha = scanBase.sha;
   let inspectingOnlyCurrentCommit = false;
 
@@ -542,6 +542,7 @@ async function getRecentReleases(): Promise<Release[]> {
       recentReleasesByAccessKey(limit: $limit) {
         id
         name
+        version
         createdAt
         commitSha
       }
@@ -553,7 +554,7 @@ async function getRecentReleases(): Promise<Release[]> {
   return response.data.recentReleasesByAccessKey;
 }
 
-function getScanBase(candidates: Release[], currentSha: string): ScanBase {
+function getScanBase(candidates: Release[], currentSha: string, syncingVersion?: string): ScanBase {
   if (baseRef) {
     let resolvedSha: string;
     try {
@@ -566,7 +567,13 @@ function getScanBase(candidates: Release[], currentSha: string): ScanBase {
     return { kind: "base-ref", sha: resolvedSha, ref: baseRef };
   }
 
-  const scanBase = selectAutomaticScanBase(candidates, currentSha, { verifyAncestorReachable });
+  const scanBase = selectAutomaticScanBase(
+    candidates,
+    currentSha,
+    { verifyAncestorReachable },
+    undefined,
+    syncingVersion,
+  );
   if (scanBase.kind !== "first-sync") {
     return scanBase;
   }

src/scan-base.ts

@@ -46,8 +46,9 @@ export function selectAutomaticScanBase(
   currentSha: string,
   deps: FindBaseShaDeps,
   cwd: string = process.cwd(),
+  syncingVersion?: string,
 ): ScanBase {
-  const result = findBaseSha(candidates, currentSha, deps);
+  const result = findBaseSha(candidates, currentSha, deps, syncingVersion);
   if (result.kind === "found") {
     return { kind: "release", sha: result.sha };
   }