fix: harden salvaged worktree include checks

Use Path.relative_to-based containment checks for the salvaged .worktreeinclude guard, remove the replayed test logic from the cherry-picked PR, and add real integration regressions for file, directory, and symlink escapes.

tests/test_worktree_security.py

@@ -0,0 +1,130 @@
+"""Security-focused integration tests for CLI worktree setup."""
+
+import subprocess
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def git_repo(tmp_path):
+    """Create a temporary git repo for testing real cli._setup_worktree behavior."""
+    repo = tmp_path / "test-repo"
+    repo.mkdir()
+    subprocess.run(["git", "init"], cwd=repo, check=True, capture_output=True)
+    subprocess.run(["git", "config", "user.email", "test@test.com"], cwd=repo, check=True, capture_output=True)
+    subprocess.run(["git", "config", "user.name", "Test"], cwd=repo, check=True, capture_output=True)
+    (repo / "README.md").write_text("# Test Repo\n")
+    subprocess.run(["git", "add", "."], cwd=repo, check=True, capture_output=True)
+    subprocess.run(["git", "commit", "-m", "Initial commit"], cwd=repo, check=True, capture_output=True)
+    return repo
+
+
+def _force_remove_worktree(info: dict | None) -> None:
+    if not info:
+        return
+    subprocess.run(
+        ["git", "worktree", "remove", info["path"], "--force"],
+        cwd=info["repo_root"],
+        capture_output=True,
+        check=False,
+    )
+    subprocess.run(
+        ["git", "branch", "-D", info["branch"]],
+        cwd=info["repo_root"],
+        capture_output=True,
+        check=False,
+    )
+
+
+class TestWorktreeIncludeSecurity:
+    def test_rejects_parent_directory_file_traversal(self, git_repo):
+        import cli as cli_mod
+
+        outside_file = git_repo.parent / "sensitive.txt"
+        outside_file.write_text("SENSITIVE DATA")
+        (git_repo / ".worktreeinclude").write_text("../sensitive.txt\n")
+
+        info = None
+        try:
+            info = cli_mod._setup_worktree(str(git_repo))
+            assert info is not None
+
+            wt_path = Path(info["path"])
+            assert not (wt_path.parent / "sensitive.txt").exists()
+            assert not (wt_path / "../sensitive.txt").resolve().exists()
+        finally:
+            _force_remove_worktree(info)
+
+    def test_rejects_parent_directory_directory_traversal(self, git_repo):
+        import cli as cli_mod
+
+        outside_dir = git_repo.parent / "outside-dir"
+        outside_dir.mkdir()
+        (outside_dir / "secret.txt").write_text("SENSITIVE DIR DATA")
+        (git_repo / ".worktreeinclude").write_text("../outside-dir\n")
+
+        info = None
+        try:
+            info = cli_mod._setup_worktree(str(git_repo))
+            assert info is not None
+
+            wt_path = Path(info["path"])
+            escaped_dir = wt_path.parent / "outside-dir"
+            assert not escaped_dir.exists()
+            assert not escaped_dir.is_symlink()
+        finally:
+            _force_remove_worktree(info)
+
+    def test_rejects_symlink_that_resolves_outside_repo(self, git_repo):
+        import cli as cli_mod
+
+        outside_file = git_repo.parent / "linked-secret.txt"
+        outside_file.write_text("LINKED SECRET")
+        (git_repo / "leak.txt").symlink_to(outside_file)
+        (git_repo / ".worktreeinclude").write_text("leak.txt\n")
+
+        info = None
+        try:
+            info = cli_mod._setup_worktree(str(git_repo))
+            assert info is not None
+
+            assert not (Path(info["path"]) / "leak.txt").exists()
+        finally:
+            _force_remove_worktree(info)
+
+    def test_allows_valid_file_include(self, git_repo):
+        import cli as cli_mod
+
+        (git_repo / ".env").write_text("SECRET=***\n")
+        (git_repo / ".worktreeinclude").write_text(".env\n")
+
+        info = None
+        try:
+            info = cli_mod._setup_worktree(str(git_repo))
+            assert info is not None
+
+            copied = Path(info["path"]) / ".env"
+            assert copied.exists()
+            assert copied.read_text() == "SECRET=***\n"
+        finally:
+            _force_remove_worktree(info)
+
+    def test_allows_valid_directory_include(self, git_repo):
+        import cli as cli_mod
+
+        assets_dir = git_repo / ".venv" / "lib"
+        assets_dir.mkdir(parents=True)
+        (assets_dir / "marker.txt").write_text("venv marker")
+        (git_repo / ".worktreeinclude").write_text(".venv\n")
+
+        info = None
+        try:
+            info = cli_mod._setup_worktree(str(git_repo))
+            assert info is not None
+
+            linked_dir = Path(info["path"]) / ".venv"
+            assert linked_dir.is_symlink()
+            assert (linked_dir / "lib" / "marker.txt").read_text() == "venv marker"
+        finally:
+            _force_remove_worktree(info)