feat(FN-4646): complete Step 2 — capture landed files at merge time

Fusion-Task-Id: FN-4646
Fusion-Task-Lineage: f921098e-3407-40fa-984d-720e0c3248c7

packages/core/src/store.ts

@@ -5297,6 +5297,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     let filesChanged: number | undefined;
     let insertions: number | undefined;
     let deletions: number | undefined;
+    let landedFiles: string[] | undefined;
 
     const headResult = await this.runGitCommand("git rev-parse HEAD");
     if (headResult.exitCode === 0) {
@@ -5321,8 +5322,22 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       deletions = undefined;
     }
 
+    if (commitSha) {
+      const landedFilesResult = await this.runGitCommand(`git show --name-only --format= "${commitSha}"`);
+      if (landedFilesResult.exitCode === 0) {
+        const parsedLandedFiles = landedFilesResult.stdout
+          .split(/\r?\n/)
+          .map((line) => line.trim())
+          .filter(Boolean);
+        if (parsedLandedFiles.length > 0) {
+          landedFiles = Array.from(new Set(parsedLandedFiles));
+        }
+      }
+    }
+
     return {
       commitSha,
+      landedFiles,
       filesChanged,
       insertions,
       deletions,
@@ -5447,6 +5462,9 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         result.merged = true;
         const mergeDetails = await this.collectMergeDetails(id, branch, task, mergeCommitMessage, mergeTarget);
         task.mergeDetails = mergeDetails;
+        if (mergeDetails.landedFiles && mergeDetails.landedFiles.length > 0) {
+          task.modifiedFiles = mergeDetails.landedFiles;
+        }
         Object.assign(result, mergeDetails);
       } else {
         // Squash conflict — reset and report

packages/engine/src/__tests__/merger-landed-files-capture.test.ts

@@ -0,0 +1,91 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { createMockStore, mockedCreateFnAgent, mockedExecSync, mockedExistsSync, type Task } from "./merger-test-helpers.js";
+import * as mergerModule from "../merger.js";
+
+describe("FN-4646 aiMergeTask landedFiles capture", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockedExistsSync.mockReturnValue(true);
+    mockedCreateFnAgent.mockResolvedValue({ session: { prompt: vi.fn().mockResolvedValue(undefined), dispose: vi.fn() } } as any);
+  });
+
+  function makeStore(settings: Record<string, unknown> = {}) {
+    const store = createMockStore(
+      { id: "FN-4646", worktree: "/tmp/root/.worktrees/FN-4646" },
+      [{ id: "FN-4646", worktree: "/tmp/root/.worktrees/FN-4646", column: "in-review" } as Task],
+    );
+    (store.getSettings as any).mockResolvedValue({ includeTaskIdInCommit: true, mergeConflictStrategy: "smart-prefer-main", ...settings });
+    return store;
+  }
+
+  it("captures squash landedFiles and overwrites modifiedFiles", async () => {
+    const store = makeStore();
+    mockedExecSync.mockImplementation((cmd: any) => {
+      const s = String(cmd);
+      if (s.includes("rev-parse --verify")) return Buffer.from("abc123");
+      if (s === "git rev-parse HEAD" || s.startsWith("git rev-parse HEAD ")) return "mergedsha123";
+      if (s.includes("git log")) return "- feat: summary";
+      if (s.includes("merge-base")) return Buffer.from("base123");
+      if (s.includes("merge --squash")) return Buffer.from("");
+      if (s.includes("diff --cached --quiet")) return "1";
+      if (s.includes("diff --cached")) return "0";
+      if (s.includes("show --shortstat --format= HEAD")) return "2 files changed, 3 insertions(+), 1 deletion(-)";
+      if (s.includes("show --name-only --format= \"mergedsha123\"")) return "a.ts\nb.ts\n";
+      if (s.includes("branch -d") || s.includes("branch -D") || s.includes("worktree remove")) return Buffer.from("");
+      return Buffer.from("");
+    });
+
+    await mergerModule.aiMergeTask(store, "/tmp/root", "FN-4646");
+    const detailsUpdate = (store.updateTask as any).mock.calls.find((call: any[]) => call[1]?.mergeDetails?.commitSha === "mergedsha123");
+    expect(detailsUpdate?.[1].mergeDetails.landedFiles).toEqual(["a.ts", "b.ts"]);
+    expect(detailsUpdate?.[1].modifiedFiles).toEqual(["a.ts", "b.ts"]);
+  });
+
+  it("captures rebase landedFiles from rebaseBaseSha..commitSha", async () => {
+    const store = makeStore({ directMergeCommitStrategy: "always-rebase" });
+    mockedExecSync.mockImplementation((cmd: any) => {
+      const s = String(cmd);
+      if (s.includes("rev-parse --verify")) return Buffer.from("abc123");
+      if (s === "git rev-parse HEAD" || s.startsWith("git rev-parse HEAD ")) return "rebasesha123";
+      if (s.includes("git log")) return "- feat: summary";
+      if (s.includes("merge-base")) return Buffer.from("abc123");
+      if (s.includes("rev-parse \"abc123\"")) return "rebasebase123";
+      if (s.includes("rev-list --reverse \"rebasebase123..fusion/FN-4646\"")) return "";
+      if (s.includes("status --porcelain")) return "";
+      if (s.includes("rev-parse --git-path CHERRY_PICK_HEAD")) return ".git/CHERRY_PICK_HEAD";
+      if (s.includes("rev-parse --git-path sequencer")) return ".git/sequencer";
+      if (s.includes("diff --shortstat \"rebasebase123..HEAD\"")) return "2 files changed, 4 insertions(+), 1 deletion(-)";
+      if (s.includes("diff --name-only \"rebasebase123..rebasesha123\"")) return "c.ts\nd.ts\n";
+      if (s.includes("branch -d") || s.includes("branch -D") || s.includes("worktree remove")) return Buffer.from("");
+      return Buffer.from("");
+    });
+
+    await mergerModule.aiMergeTask(store, "/tmp/root", "FN-4646");
+    const detailsUpdate = (store.updateTask as any).mock.calls.find((call: any[]) => call[1]?.mergeDetails?.commitSha === "rebasesha123");
+    expect(detailsUpdate?.[1].mergeDetails.rebaseBaseSha).toBe("rebasebase123");
+    expect(detailsUpdate?.[1].mergeDetails.landedFiles).toEqual(["c.ts", "d.ts"]);
+    expect(detailsUpdate?.[1].modifiedFiles).toEqual(["c.ts", "d.ts"]);
+  });
+
+  it("skips landedFiles capture for mergeWasEmpty", async () => {
+    const store = makeStore();
+    mockedExecSync.mockImplementation((cmd: any) => {
+      const s = String(cmd);
+      if (s.includes("rev-parse --verify")) return Buffer.from("abc123");
+      if (s === "git rev-parse HEAD" || s.startsWith("git rev-parse HEAD ")) return "mergedsha123";
+      if (s.includes("git log")) return "- feat: summary";
+      if (s.includes("merge-base")) return Buffer.from("base123");
+      if (s.includes("merge --squash")) return Buffer.from("");
+      if (s.includes("diff --cached --quiet")) return "0";
+      if (s.includes("show --shortstat --format= HEAD")) return "2 files changed, 3 insertions(+), 1 deletion(-)";
+      if (s.includes("branch -d") || s.includes("branch -D") || s.includes("worktree remove")) return Buffer.from("");
+      return Buffer.from("");
+    });
+
+    await mergerModule.aiMergeTask(store, "/tmp/root", "FN-4646");
+    const detailsUpdate = (store.updateTask as any).mock.calls.find((call: any[]) => call[1]?.mergeDetails);
+    expect(detailsUpdate?.[1].mergeDetails.commitSha).toBeUndefined();
+    expect(detailsUpdate?.[1].mergeDetails.landedFiles).toBeUndefined();
+    expect(detailsUpdate?.[1].modifiedFiles).toBeUndefined();
+  });
+});

packages/engine/src/merger.ts

@@ -7073,6 +7073,7 @@ export async function aiMergeTask(
     let filesChanged: number | undefined;
     let insertions: number | undefined;
     let deletions: number | undefined;
+    let landedFiles: string[] | undefined;
 
     try {
       const statsCommand = selectedPostMergeAuditStrategy === "rebase" && rebaseMergeBaseSha
@@ -7192,9 +7193,32 @@ export async function aiMergeTask(
     const recordedInsertions = mergeWasEmpty ? 0 : insertions;
     const recordedDeletions = mergeWasEmpty ? 0 : deletions;
 
+    if (!isEmptyCommit && !mergeWasEmpty && recordedSha) {
+      try {
+        const landedFilesCommand = selectedPostMergeAuditStrategy === "rebase" && rebaseMergeBaseSha
+          ? `git diff --name-only ${quoteArg(`${rebaseMergeBaseSha}..${recordedSha}`)}`
+          : `git show --name-only --format= ${quoteArg(recordedSha)}`;
+        const { stdout: landedFilesOutput } = await execAsync(landedFilesCommand, {
+          cwd: rootDir,
+          encoding: "utf-8",
+          maxBuffer: 2 * 1024 * 1024,
+        });
+        const parsedLandedFiles = landedFilesOutput
+          .split(/\r?\n/)
+          .map((line) => line.trim())
+          .filter(Boolean);
+        if (parsedLandedFiles.length > 0) {
+          landedFiles = Array.from(new Set(parsedLandedFiles));
+        }
+      } catch {
+        // non-fatal
+      }
+    }
+
     const mergeDetails: MergeDetails = {
       commitSha: recordedSha,
       rebaseBaseSha: selectedPostMergeAuditStrategy === "rebase" && !mergeWasEmpty ? rebaseMergeBaseSha : undefined,
+      landedFiles,
       filesChanged: recordedFilesChanged,
       insertions: recordedInsertions,
       deletions: recordedDeletions,
@@ -7209,7 +7233,10 @@ export async function aiMergeTask(
       autoResolvedCount: result.autoResolvedCount,
     };
 
-    await store.updateTask(taskId, { mergeDetails });
+    await store.updateTask(taskId, {
+      mergeDetails,
+      modifiedFiles: landedFiles && landedFiles.length > 0 ? landedFiles : undefined,
+    });
     if (recordedSha) {
       const currentTask = await store.getTask(taskId);
       if (currentTask?.lineageId) {