bug: handle git changes outside the workspace root

bough/analyzer.py

@@ -165,7 +165,11 @@ def _find_direct_packages(
         directly_affected = set()
         strip_prefix = self.workspace_root.relative_to(self.repo_root)
         for file_path in changed_files:
-            file_path_obj = Path(file_path).relative_to(strip_prefix)
+            if Path(file_path).is_relative_to(strip_prefix):
+                file_path_obj = Path(file_path).relative_to(strip_prefix)
+            else:
+                logger.debug(f"Ignoring file {file_path} outside of workspace")
+                continue
 
             if self._matches_patterns(file_path, self.config.ignore):
                 logger.debug(f"Ignoring file {file_path} (matches ignore patterns)")

pyproject.toml

@@ -31,7 +31,7 @@ dev = [
     "pytest-cov>=7.0.0",
     "ruff>=0.12.11",
     "tomli-w>=1.0.0",
-    "ty>=0.0.1a25",
+    "ty>=0.0.15",
 ]
 
 [tool.ruff]

tests/test_complex_scenarios.py

@@ -3,6 +3,7 @@
 from pathlib import Path
 from unittest.mock import Mock, patch
 
+import pytest
 import tomli_w
 
 from bough.analyzer import BoughAnalyzer
@@ -409,3 +410,29 @@ def test_divergent_git_vs_workspace_roots(mock_repo_class, tmp_path):
     affected, _ = analyzer.find_affected()
 
     assert affected == {"web"}
+
+
+@pytest.mark.parametrize(
+    "changed_file",
+    ["frontend/foo", "Dockerfile", ".github/workflows/ci.yaml"],
+)
+@patch("git.Repo")
+def test_changed_files_outside_workspace(mock_repo_class, tmp_path, changed_file):
+    """Test that files outside the workspace do not trigger any builds."""
+    structure = {
+        "tools/cli": {"dependencies": []},
+    }
+
+    create_workspace_structure(tmp_path / "backend", structure)
+
+    config_path = tmp_path / ".bough.yml"
+    config_path.write_text("""
+buildable:
+  - "tools/*"
+""")
+
+    mock_repo_class.return_value = mock_git_changes([changed_file])
+    analyzer = BoughAnalyzer.from_workspace(tmp_path, tmp_path / "backend", config_path)
+    affected, _ = analyzer.find_affected()
+
+    assert affected == set()

tests/test_formatters.py

@@ -77,7 +77,7 @@ def package_graph(draw):
     return packages
 
 
-@given(package_graph())
+@given(package_graph())  # ty: ignore[missing-argument]
 def test_dependency_graph_contains_all_packages(packages):
     """All package names must appear in dependency graph output."""
     analyzer = Mock()