fix(cli): apply --files startup seed in virtual shell

src/cli/shell-files.test.ts

@@ -0,0 +1,48 @@
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { Bash } from "../Bash.js";
+import { OverlayFs } from "../fs/overlay-fs/overlay-fs.js";
+import { seedOverlayFiles } from "./shell-files.js";
+
+describe("seedOverlayFiles", () => {
+  let tempDir: string;
+
+  beforeEach(() => {
+    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "just-bash-shell-files-"));
+    fs.writeFileSync(path.join(tempDir, "real.txt"), "from-disk");
+  });
+
+  afterEach(() => {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  });
+
+  it("seeds overlay-only files for shell startup", async () => {
+    const overlayFs = new OverlayFs({ root: tempDir, mountPoint: "/" });
+    seedOverlayFiles(overlayFs, {
+      "/seeded.txt": "from-seed",
+      "nested/seeded2.txt": "from-seed-2",
+    });
+
+    const env = new Bash({ fs: overlayFs, cwd: "/" });
+    const one = await env.exec("cat /seeded.txt");
+    const two = await env.exec("cat /nested/seeded2.txt");
+
+    expect(one.exitCode).toBe(0);
+    expect(one.stdout).toBe("from-seed");
+    expect(two.exitCode).toBe(0);
+    expect(two.stdout).toBe("from-seed-2");
+  });
+
+  it("does nothing when files are omitted", async () => {
+    const overlayFs = new OverlayFs({ root: tempDir, mountPoint: "/" });
+    seedOverlayFiles(overlayFs, undefined);
+
+    const env = new Bash({ fs: overlayFs, cwd: "/" });
+    const result = await env.exec("cat /seeded.txt");
+
+    expect(result.exitCode).toBe(1);
+    expect(result.stderr).toContain("No such file or directory");
+  });
+});

src/cli/shell-files.ts

@@ -0,0 +1,15 @@
+import type { OverlayFs } from "../fs/overlay-fs/overlay-fs.js";
+
+/**
+ * Seed in-memory overlay files for shell startup fixtures.
+ * Paths are virtual shell paths (e.g. "/tmp/data.txt").
+ */
+export function seedOverlayFiles(
+  overlayFs: OverlayFs,
+  files?: Record<string, string>,
+): void {
+  if (!files) return;
+  for (const [path, content] of Object.entries(files)) {
+    overlayFs.writeFileSync(path, content);
+  }
+}

src/cli/shell.ts

@@ -12,6 +12,7 @@ import * as readline from "node:readline";
 import { Bash } from "../Bash.js";
 import { OverlayFs } from "../fs/overlay-fs/overlay-fs.js";
 import { getErrorMessage } from "../interpreter/helpers/errors.js";
+import { seedOverlayFiles } from "./shell-files.js";
 
 // ANSI colors
 const colors = {
@@ -47,6 +48,7 @@ class VirtualShell {
       root,
       mountPoint: "/",
     });
+    seedOverlayFiles(overlayFs, options.files);
 
     this.env = new Bash({
       fs: overlayFs,