feat(FN-4222): complete Step 2 — extend git ops for finalize

Fusion-Task-Id: FN-4222
Fusion-Task-Lineage: 7de6b18c-36d5-49e8-bbd7-084707e88d6a

packages/engine/src/__tests__/finalize-git-ops.test.ts

@@ -0,0 +1,57 @@
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { execSync } from "node:child_process";
+import { describe, expect, it } from "vitest";
+import { defaultGitOps } from "../experiment/git-ops.js";
+
+function createRepo() {
+  const dir = mkdtempSync(join(tmpdir(), "finalize-git-ops-"));
+  execSync("git init", { cwd: dir });
+  execSync("git config user.email test@example.com", { cwd: dir });
+  execSync("git config user.name Test", { cwd: dir });
+  writeFileSync(join(dir, "file.txt"), "one\n");
+  execSync("git add file.txt", { cwd: dir });
+  execSync('git commit -m "first"', { cwd: dir });
+  writeFileSync(join(dir, "file.txt"), "two\n");
+  execSync("git add file.txt", { cwd: dir });
+  execSync('git commit -m "second"', { cwd: dir });
+  return dir;
+}
+
+describe.skipIf(process.platform === "win32")("finalize git ops", () => {
+  it("supports mergeBase/branch/checkout/currentBranch/deleteBranch/cherryPick", async () => {
+    const cwd = createRepo();
+    try {
+      const git = defaultGitOps(cwd);
+      const head = await git.head();
+      const initialBranch = (await git.currentBranch()) ?? "main";
+      await git.createBranch("feature/a", head);
+      expect(await git.branchExists("feature/a")).toBe(true);
+
+      await git.checkout("feature/a");
+      expect(await git.currentBranch()).toBe("feature/a");
+
+      writeFileSync(join(cwd, "file.txt"), "feature\n");
+      await git.add(["file.txt"]);
+      const featureCommit = await git.commit("feature change");
+
+      await git.checkout(initialBranch);
+      writeFileSync(join(cwd, "main.txt"), "main\n");
+      await git.add(["main.txt"]);
+      await git.commit("main change");
+
+      const mergeBase = await git.mergeBase(initialBranch, "feature/a");
+      expect(mergeBase).toBe(head);
+
+      await git.checkout(initialBranch);
+      await git.cherryPick(featureCommit);
+      expect((await git.statusPorcelain()).trim()).toBe("");
+
+      await git.deleteBranch("feature/a", { force: true });
+      expect(await git.branchExists("feature/a")).toBe(false);
+    } finally {
+      rmSync(cwd, { recursive: true, force: true });
+    }
+  });
+});