Show recent commit history in the explorer (#2312)

* feat(app): show recent commit history in explorer

* fix(app): keep recent commit history accurate

* fix(app): include merged commits in recent history

* perf(app): bound recent commit classification

* fix(app): refresh recent commits on Git updates

packages/app/src/git/checkout-status-cache.test.ts

@@ -2,7 +2,11 @@
 import { QueryClient } from "@tanstack/react-query";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import type { CheckoutStatusUpdate } from "@getpaseo/protocol/messages";
-import { checkoutPrStatusQueryKey, checkoutStatusQueryKey } from "@/git/query-keys";
+import {
+  checkoutCommitsQueryKey,
+  checkoutPrStatusQueryKey,
+  checkoutStatusQueryKey,
+} from "@/git/query-keys";
 import {
   prPanePipelineQueryKey,
   prPaneTimelineQueryKey,
@@ -132,6 +136,25 @@ describe("applyCheckoutStatusUpdateFromEvent", () => {
     expect(queryClient.getQueryData(checkoutStatusQueryKey(serverId, cwd))).toEqual(pushed);
   });
 
+  it("invalidates recent commits when checkout status is pushed", () => {
+    const queryClient = createQueryClient();
+    queryClient.setQueryData(checkoutCommitsQueryKey(serverId, cwd), { commits: [] });
+    queryClient.setQueryData(checkoutCommitsQueryKey(serverId, "/repo2"), { commits: [] });
+
+    applyCheckoutStatusUpdateFromEvent({
+      queryClient,
+      serverId,
+      message: checkoutStatusUpdate(checkoutStatus()),
+    });
+
+    expect(queryClient.getQueryState(checkoutCommitsQueryKey(serverId, cwd))?.isInvalidated).toBe(
+      true,
+    );
+    expect(
+      queryClient.getQueryState(checkoutCommitsQueryKey(serverId, "/repo2"))?.isInvalidated,
+    ).toBe(false);
+  });
+
   it("writes the PR status cache when prStatus is present, and skips it otherwise", () => {
     const queryClient = createQueryClient();
     const pushedPr = prStatus({ requestId: "pr-1" });

packages/app/src/git/checkout-status-cache.ts

@@ -2,6 +2,7 @@ import type { QueryClient } from "@tanstack/react-query";
 import type { CheckoutStatusResponse, CheckoutStatusUpdate } from "@getpaseo/protocol/messages";
 import equal from "fast-deep-equal/es6";
 import {
+  checkoutCommitsQueryKey,
   checkoutPrStatusQueryKey,
   checkoutStatusQueryKey,
   invalidatePrPaneTimelineForCheckout,
@@ -49,6 +50,9 @@ export function applyCheckoutStatusUpdateFromEvent({
     : undefined;
   const cachePayload = prStatus ? { ...payload, prStatus } : payload;
   queryClient.setQueryData(checkoutStatusQueryKey(serverId, payload.cwd), cachePayload);
+  void queryClient.invalidateQueries({
+    queryKey: checkoutCommitsQueryKey(serverId, payload.cwd),
+  });
   expireStaleDiffModeOverrides({
     serverId,
     cwd: payload.cwd,

packages/app/src/git/query-keys.test.ts

@@ -2,6 +2,7 @@ import { QueryClient } from "@tanstack/react-query";
 import { describe, expect, it } from "vitest";
 import {
   checkoutDiffQueryKey,
+  checkoutCommitsQueryKey,
   checkoutPrStatusQueryKey,
   checkoutStatusQueryKey,
   invalidateCheckoutGitQueriesForClient,
@@ -24,6 +25,8 @@ describe("checkout query keys", () => {
       files: [],
     });
     queryClient.setQueryData(checkoutPrStatusQueryKey(serverId, cwd), { status: { number: 12 } });
+    queryClient.setQueryData(checkoutCommitsQueryKey(serverId, cwd), { commits: [] });
+    queryClient.setQueryData(checkoutCommitsQueryKey(serverId, "/tmp/other"), { commits: [] });
     queryClient.setQueryData(prPaneTimelineQueryKey({ serverId, cwd, prNumber: 12 }), {
       items: [],
     });
@@ -62,6 +65,12 @@ describe("checkout query keys", () => {
     expect(queryClient.getQueryState(checkoutPrStatusQueryKey(serverId, cwd))?.isInvalidated).toBe(
       true,
     );
+    expect(queryClient.getQueryState(checkoutCommitsQueryKey(serverId, cwd))?.isInvalidated).toBe(
+      true,
+    );
+    expect(
+      queryClient.getQueryState(checkoutCommitsQueryKey(serverId, "/tmp/other"))?.isInvalidated,
+    ).toBe(false);
     expect(
       queryClient.getQueryState(prPaneTimelineQueryKey({ serverId, cwd, prNumber: 12 }))
         ?.isInvalidated,
@@ -102,6 +111,8 @@ describe("checkout query keys", () => {
     queryClient.setQueryData(checkoutStatusQueryKey(serverId, cwd), { isGit: true });
     queryClient.setQueryData(checkoutStatusQueryKey(serverId, otherCwd), { isGit: true });
     queryClient.setQueryData(checkoutPrStatusQueryKey(serverId, cwd), { status: { number: 12 } });
+    queryClient.setQueryData(checkoutCommitsQueryKey(serverId, cwd), { commits: [] });
+    queryClient.setQueryData(checkoutCommitsQueryKey(otherServerId, cwd), { commits: [] });
     queryClient.setQueryData(prPaneTimelineQueryKey({ serverId, cwd, prNumber: 12 }), {
       items: [],
     });
@@ -128,6 +139,12 @@ describe("checkout query keys", () => {
     expect(queryClient.getQueryState(checkoutPrStatusQueryKey(serverId, cwd))?.isInvalidated).toBe(
       true,
     );
+    expect(queryClient.getQueryState(checkoutCommitsQueryKey(serverId, cwd))?.isInvalidated).toBe(
+      true,
+    );
+    expect(
+      queryClient.getQueryState(checkoutCommitsQueryKey(otherServerId, cwd))?.isInvalidated,
+    ).toBe(false);
     expect(
       queryClient.getQueryState(prPaneTimelineQueryKey({ serverId, cwd, prNumber: 12 }))
         ?.isInvalidated,

packages/app/src/git/query-keys.ts

@@ -62,6 +62,9 @@ export async function invalidateCheckoutGitQueriesForClient(
     queryClient.invalidateQueries({
       predicate: checkoutQueryPredicate("checkoutPrStatus", identity),
     }),
+    queryClient.invalidateQueries({
+      queryKey: checkoutCommitsQueryKey(identity.serverId, identity.cwd),
+    }),
     queryClient.invalidateQueries({
       predicate: checkoutQueryPredicate(prPaneTimelineQueryKind, identity),
     }),
@@ -81,6 +84,7 @@ export async function invalidateCheckoutGitQueriesForServer(
   const kinds = [
     "checkoutStatus",
     "checkoutPrStatus",
+    "checkoutCommits",
     prPaneTimelineQueryKind,
     prPanePipelineQueryKind,
   ];

packages/app/src/i18n/resources/ar.ts

@@ -788,12 +788,12 @@ export const ar: TranslationResources = {
         deletedFile: "تم الحذف",
         commits: {
           title: "الإيداعات",
-          countLabel: "{{count}} إيداعات قبل الأساس",
+          countLabel: "{{count}} من الإيداعات الأخيرة",
           fileDiffEmpty: "لا توجد تغييرات لعرضها",
           fileDiffError: "تعذّر تحميل فروق الملف",
           loading: "جارٍ تحميل الإيداعات…",
           loadError: "تعذّر تحميل الإيداعات",
-          empty: "لا توجد إيداعات قبل الأساس",
+          empty: "لا توجد إيداعات بعد",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/en.ts

@@ -798,12 +798,12 @@ export const en = {
         deletedFile: "Deleted",
         commits: {
           title: "Commits",
-          countLabel: "{{count}} commits ahead of base",
+          countLabel: "{{count}} recent commits",
           fileDiffEmpty: "No changes to display",
           fileDiffError: "Failed to load file diff",
           loading: "Loading commits…",
           loadError: "Failed to load commits",
-          empty: "No commits ahead of base",
+          empty: "No commits yet",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/es.ts

@@ -819,12 +819,12 @@ export const es: TranslationResources = {
         deletedFile: "Eliminado",
         commits: {
           title: "Commits",
-          countLabel: "{{count}} commits por delante de la base",
+          countLabel: "{{count}} commits recientes",
           fileDiffEmpty: "No hay cambios para mostrar",
           fileDiffError: "Error al cargar el diff del archivo",
           loading: "Cargando commits…",
           loadError: "Error al cargar los commits",
-          empty: "No hay commits por delante de la base",
+          empty: "Aún no hay commits",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/fr.ts

@@ -818,12 +818,12 @@ export const fr: TranslationResources = {
         deletedFile: "Supprimé",
         commits: {
           title: "Commits",
-          countLabel: "{{count}} commits en avance sur la base",
+          countLabel: "{{count}} commits récents",
           fileDiffEmpty: "Aucune modification à afficher",
           fileDiffError: "Échec du chargement du diff du fichier",
           loading: "Chargement des commits…",
           loadError: "Échec du chargement des commits",
-          empty: "Aucun commit en avance sur la base",
+          empty: "Aucun commit pour le moment",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/ja.ts

@@ -799,12 +799,12 @@ export const ja: TranslationResources = {
         deletedFile: "削除済み",
         commits: {
           title: "コミット",
-          countLabel: "ベースより先のコミット数: {{count}}",
+          countLabel: "最近のコミット数: {{count}}",
           fileDiffEmpty: "表示する変更はありません",
           fileDiffError: "ファイル差分の読み込みに失敗しました",
           loading: "コミットを読み込み中…",
           loadError: "コミットの読み込みに失敗しました",
-          empty: "ベースより先のコミットはありません",
+          empty: "コミットはまだありません",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/pt-BR.ts

@@ -810,12 +810,12 @@ export const ptBR: TranslationResources = {
         deletedFile: "Excluído",
         commits: {
           title: "Commits",
-          countLabel: "{{count}} commits à frente da base",
+          countLabel: "{{count}} commits recentes",
           fileDiffEmpty: "Nenhuma alteração para exibir",
           fileDiffError: "Falha ao carregar diff do arquivo",
           loading: "Carregando commits…",
           loadError: "Falha ao carregar commits",
-          empty: "Nenhum commit à frente da base",
+          empty: "Ainda não há commits",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/ru.ts

@@ -810,12 +810,12 @@ export const ru: TranslationResources = {
         deletedFile: "Удалено",
         commits: {
           title: "Коммиты",
-          countLabel: "{{count}} коммитов впереди базы",
+          countLabel: "{{count}} последних коммитов",
           fileDiffEmpty: "Нет изменений для отображения",
           fileDiffError: "Не удалось загрузить различия файла",
           loading: "Загрузка коммитов…",
           loadError: "Не удалось загрузить коммиты",
-          empty: "Нет коммитов впереди базы",
+          empty: "Коммитов пока нет",
         },
       },
       openInEditor: {

packages/app/src/i18n/resources/zh-CN.ts

@@ -780,12 +780,12 @@ export const zhCN: TranslationResources = {
         deletedFile: "已删除",
         commits: {
           title: "提交",
-          countLabel: "领先基线 {{count}} 个提交",
+          countLabel: "最近 {{count}} 个提交",
           fileDiffEmpty: "没有可显示的更改",
           fileDiffError: "加载文件差异失败",
           loading: "正在加载提交…",
           loadError: "加载提交失败",
-          empty: "没有领先基线的提交",
+          empty: "暂无提交",
         },
       },
       openInEditor: {

packages/server/src/utils/checkout-git.commit-file-diff.test.ts

@@ -88,4 +88,22 @@ describe("getCommitFileDiff", () => {
 
     expect(file).toBeNull();
   });
+
+  it("returns a merge commit diff against its first parent", async () => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "README.md", "base\n", "initial");
+    git(["checkout", "-b", "feature"], repoDir);
+    commitFile(repoDir, "feature.txt", "feature\n", "add feature");
+    git(["checkout", "main"], repoDir);
+    commitFile(repoDir, "main.txt", "main\n", "advance main");
+    git(["merge", "--no-ff", "feature", "-m", "merge feature"], repoDir);
+    const sha = headSha(repoDir);
+
+    const file = await getCommitFileDiff({ cwd: repoDir, sha, path: "feature.txt" });
+
+    expect(file?.path).toBe("feature.txt");
+    expect(file?.isNew).toBe(true);
+    expect(file?.additions).toBe(1);
+    expect(file?.deletions).toBe(0);
+  });
 });

packages/server/src/utils/checkout-git.commits.test.ts

@@ -52,7 +52,7 @@ function addBareRemote(repoDir: string, tempDir: string): string {
 }
 
 describe("listCheckoutCommits", () => {
-  it("lists commits ahead of base newest-first with on-remote flags and file stats", async () => {
+  it("lists recent commits newest-first with on-remote flags and file stats", async () => {
     const { repoDir, tempDir } = initRepoOnMain();
     git(["checkout", "-b", "feature"], repoDir);
     commitFile(repoDir, "foo.txt", "a\nb\nc\n", "Add foo");
@@ -65,12 +65,14 @@ describe("listCheckoutCommits", () => {
     const { baseRef, commits } = await listCheckoutCommits({ cwd: repoDir });
 
     expect(baseRef).toBe("main");
-    expect(commits).toHaveLength(2);
+    expect(commits).toHaveLength(3);
     expect(commits[0]?.subject).toBe("Add bar");
     expect(commits[1]?.subject).toBe("Add foo");
+    expect(commits[2]?.subject).toBe("initial");
 
     expect(commits[0]?.isOnRemote).toBe(false);
     expect(commits[1]?.isOnRemote).toBe(true);
+    expect(commits[2]?.isOnRemote).toBe(true);
 
     expect(commits[0]?.files).toEqual([
       { path: "bar.txt", additions: 1, deletions: 0, status: "added" },
@@ -85,11 +87,11 @@ describe("listCheckoutCommits", () => {
     expect(Number.isNaN(new Date(commits[0]?.authorDate ?? "").getTime())).toBe(false);
   });
 
-  it("returns [] when there are no commits ahead of base", async () => {
+  it("shows recent history on the base branch", async () => {
     const { repoDir } = initRepoOnMain();
     const { baseRef, commits } = await listCheckoutCommits({ cwd: repoDir });
     expect(baseRef).toBeNull();
-    expect(commits).toEqual([]);
+    expect(commits.map((entry) => entry.subject)).toEqual(["initial"]);
   });
 
   it("marks all commits local-only when there is no remote", async () => {
@@ -101,10 +103,61 @@ describe("listCheckoutCommits", () => {
     const { baseRef, commits } = await listCheckoutCommits({ cwd: repoDir });
 
     expect(baseRef).toBe("main");
-    expect(commits).toHaveLength(2);
+    expect(commits).toHaveLength(3);
     expect(commits.every((c) => c.isOnRemote === false)).toBe(true);
   });
 
+  it("recognizes base history on a remote before the feature branch is pushed", async () => {
+    const { repoDir, tempDir } = initRepoOnMain();
+    addBareRemote(repoDir, tempDir);
+    git(["push", "-u", "origin", "main"], repoDir);
+    git(["checkout", "-b", "feature"], repoDir);
+    commitFile(repoDir, "feature.txt", "local\n", "Local feature");
+
+    const { commits } = await listCheckoutCommits({ cwd: repoDir });
+
+    expect(commits.map(({ subject, isOnRemote }) => ({ subject, isOnRemote }))).toEqual([
+      { subject: "Local feature", isOnRemote: false },
+      { subject: "initial", isOnRemote: true },
+    ]);
+  });
+
+  it("limits history and unpushed classification to the 20 most recent commits", async () => {
+    const { repoDir } = initRepoOnMain();
+    for (let index = 1; index <= 24; index += 1) {
+      commitFile(repoDir, "history.txt", `${index}\n`, `Commit ${index}`);
+    }
+
+    const { commits } = await listCheckoutCommits({ cwd: repoDir });
+
+    expect(commits).toHaveLength(20);
+    expect(commits.every((entry) => entry.isOnRemote === false)).toBe(true);
+    expect(commits.map((entry) => entry.subject)).toEqual(
+      Array.from({ length: 20 }, (_, index) => `Commit ${24 - index}`),
+    );
+  });
+
+  it("shows merged branch commits and compares the merge against its first parent", async () => {
+    const { repoDir } = initRepoOnMain();
+    git(["checkout", "-b", "feature"], repoDir);
+    commitFile(repoDir, "feature.txt", "feature\n", "Add feature");
+    git(["checkout", "main"], repoDir);
+    commitFile(repoDir, "main.txt", "main\n", "Advance main");
+    git(["merge", "--no-ff", "feature", "-m", "Merge feature"], repoDir);
+
+    const { commits } = await listCheckoutCommits({ cwd: repoDir });
+
+    expect(commits.map((entry) => entry.subject)).toEqual([
+      "Merge feature",
+      "Advance main",
+      "Add feature",
+      "initial",
+    ]);
+    expect(commits[0]?.files).toEqual([
+      { path: "feature.txt", additions: 1, deletions: 0, status: "added" },
+    ]);
+  });
+
   it("classifies renamed files with status renamed and correct destination path", async () => {
     const { repoDir } = initRepoOnMain();
     git(["checkout", "-b", "feature"], repoDir);

packages/server/src/utils/checkout-git.ts

@@ -2001,9 +2001,8 @@ export async function getCheckoutStatus(
   };
 }
 
-// Cap on how many ahead-of-base commits we enumerate. Branches with more than
+// The explorer is a recent-history view, not a full repository log.
-// this many unmerged commits are truncated to the newest MAX_CHECKOUT_COMMITS.
+const MAX_CHECKOUT_COMMITS = 20;
-const MAX_CHECKOUT_COMMITS = 200;
 // Bytes git emits between fields/records. We split parsed output on these.
 const COMMIT_FIELD_SEPARATOR = "\x00";
 const COMMIT_RECORD_SEPARATOR = "\x1e";
@@ -2145,41 +2144,16 @@ function parseCheckoutCommitRecords(stdout: string): ParsedCheckoutCommit[] {
   return commits;
 }
 
-async function resolveCheckoutCommitUpstreamRef(
+// Returns commits reachable from HEAD that are not reachable from any remote ref.
-  cwd: string,
+async function getUnpushedCommitShas(cwd: string, context?: CheckoutContext): Promise<Set<string>> {
-  currentBranch: string,
+  const { stdout } = await runGitCommand(
-  context?: CheckoutContext,
+    ["rev-list", `--max-count=${MAX_CHECKOUT_COMMITS}`, "HEAD", "--not", "--remotes"],
-): Promise<string | null> {
+    {
-  // Prefer the branch's configured `@{u}`. If it's configured but the
+      cwd,
-  // remote-tracking ref isn't present locally (e.g. configured upstream that was
+      envOverlay: READ_ONLY_GIT_ENV,
-  // never fetched), fall back to `origin/<branch>` when that ref does exist, so a
+      logger: context?.logger,
-  // standard `origin` push is still recognized. Both missing => no remote.
+    },
-  const configured = await getConfiguredUpstreamRef(cwd, currentBranch, context);
+  );
-  if (configured && (await doesGitRefExist(cwd, `refs/remotes/${configured}`, context))) {
-    return configured;
-  }
-  if (await doesGitRefExist(cwd, `refs/remotes/origin/${currentBranch}`, context)) {
-    return `origin/${currentBranch}`;
-  }
-  return null;
-}
-
-// Returns the set of SHAs on the current branch that are NOT on the upstream
-// (local-only/unpushed), or `null` when no upstream exists (no remote at all).
-async function getLocalOnlyCommitShas(
-  cwd: string,
-  currentBranch: string,
-  context?: CheckoutContext,
-): Promise<Set<string> | null> {
-  const upstreamRef = await resolveCheckoutCommitUpstreamRef(cwd, currentBranch, context);
-  if (!upstreamRef) {
-    return null;
-  }
-  const { stdout } = await runGitCommand(["rev-list", `${upstreamRef}..HEAD`], {
-    cwd,
-    envOverlay: READ_ONLY_GIT_ENV,
-    logger: context?.logger,
-  });
   return new Set(
     stdout
       .split("\n")
@@ -2189,13 +2163,8 @@ async function getLocalOnlyCommitShas(
 }
 
 /**
- * Lists the current branch's commits that are ahead of its base branch, newest
+ * Lists the current branch's 20 most recent commits, newest first, each flagged
- * first, each flagged local-only vs on-remote with per-commit file +/- stats.
+ * local-only vs on-remote with per-commit file +/- stats.
- *
- * Base ref is resolved exactly like {@link getCheckoutStatus}: the stored/default
- * base branch, mapped to the best comparison ref (origin/<base> when present,
- * else local <base>). Returns `[]` when the base cannot be resolved, the current
- * ref is the base itself, or there are no commits ahead.
  */
 export interface CheckoutCommitsResult {
   baseRef: string | null;
@@ -2213,21 +2182,14 @@ export async function listCheckoutCommits({
   }
 
   const { resolvedBaseRef } = await resolveBaseRefForCwd(cwd);
-  if (!resolvedBaseRef) {
+  const normalizedBaseRef = resolvedBaseRef ? normalizeLocalBranchRefName(resolvedBaseRef) : null;
-    return { baseRef: null, commits: [] };
+  let comparisonBaseRef: string | null = null;
-  }
+  if (resolvedBaseRef && normalizedBaseRef && normalizedBaseRef !== currentBranch) {
-
+    try {
-  const normalizedBaseRef = normalizeLocalBranchRefName(resolvedBaseRef);
+      comparisonBaseRef = await resolveBestComparisonBaseRef(cwd, resolvedBaseRef);
-  if (!normalizedBaseRef || normalizedBaseRef === currentBranch) {
+    } catch {
-    return { baseRef: null, commits: [] };
+      // History does not depend on the configured base being available.
-  }
+    }
-
-  let comparisonBaseRef: string;
-  try {
-    comparisonBaseRef = await resolveBestComparisonBaseRef(cwd, resolvedBaseRef);
-  } catch {
-    // Base branch is not present locally or on origin — nothing to compare against.
-    return { baseRef: null, commits: [] };
   }
 
   // Single pass: `--raw` carries the status letter, `--numstat` the +/- counts.
@@ -2235,8 +2197,8 @@ export async function listCheckoutCommits({
   const logResult = await runGitCommand(
     [
       "log",
-      `${comparisonBaseRef}..HEAD`,
+      "HEAD",
-      "--no-merges",
+      "--diff-merges=first-parent",
       `--max-count=${MAX_CHECKOUT_COMMITS}`,
       `--format=${COMMIT_LOG_FORMAT}`,
       "--raw",
@@ -2251,7 +2213,7 @@ export async function listCheckoutCommits({
     return { baseRef: comparisonBaseRef, commits: [] };
   }
 
-  const localOnlyShas = await getLocalOnlyCommitShas(cwd, currentBranch);
+  const unpushedShas = await getUnpushedCommitShas(cwd);
 
   const commits = records.map((record) => ({
     sha: record.sha,
@@ -2259,7 +2221,7 @@ export async function listCheckoutCommits({
     subject: record.subject,
     authorName: record.authorName,
     authorDate: record.authorDate,
-    isOnRemote: localOnlyShas === null ? false : !localOnlyShas.has(record.sha),
+    isOnRemote: !unpushedShas.has(record.sha),
     files: record.files,
   }));
 
@@ -2271,13 +2233,12 @@ export async function listCheckoutCommits({
  * parses it into the same {@link ParsedDiffFile} shape the diff subscription
  * emits (so the client can reuse its existing renderer).
  *
- * Runs `git show <sha> --format= -- <path>` with the sha and path passed as
+ * Compares merge commits to their first parent, matching the linear history shown
- * separate process args (never interpolated into a shell string), and `--format=`
+ * in the explorer. The text is parsed and highlighted by
- * suppresses the commit header so the output is a pure unified diff. The text is
+ * {@link parseAndHighlightDiff} — the exact parser the diff subscription uses.
- * parsed and highlighted by {@link parseAndHighlightDiff} — the exact parser the
+ * Returns `null` when the file is absent from the commit or the change is
- * diff subscription uses. Returns `null` when the file is absent from the commit
+ * binary-only (no textual hunks). Throws on git failure (e.g. an unknown sha),
- * or the change is binary-only (no textual hunks). Throws on git failure (e.g. an
+ * which the caller maps to a typed checkout error.
- * unknown sha), which the caller maps to a typed checkout error.
  */
 export async function getCommitFileDiff({
   cwd,
@@ -2288,10 +2249,13 @@ export async function getCommitFileDiff({
   sha: string;
   path: string;
 }): Promise<ParsedDiffFile | null> {
-  const { stdout } = await runGitCommand(["show", sha, "--format=", "--", path], {
+  const { stdout } = await runGitCommand(
-    cwd,
+    ["show", sha, "--format=", "--diff-merges=first-parent", "--", path],
-    envOverlay: READ_ONLY_GIT_ENV,
+    {
-  });
+      cwd,
+      envOverlay: READ_ONLY_GIT_ENV,
+    },
+  );
 
   if (stdout.trim().length === 0) {
     return null;