patch: Anchor never-patch matcher to full path (closes #47)

src/fips_agents_cli/tools/patching.py

@@ -1,6 +1,7 @@
 """Utilities for patching projects with template updates."""
 
 import difflib
+import fnmatch
 import json
 import shutil
 import tempfile
@@ -555,12 +556,23 @@ def _files_identical(file1: Path, file2: Path) -> bool:
 
 
 def _should_never_patch(file_path: Path, never_patch: list[str]) -> bool:
-    """Check if a file should never be patched, given the rule list."""
+    """Return True when ``file_path`` matches any never-patch pattern.
+
+    Patterns are matched against the full relative path with
+    :func:`fnmatch.fnmatchcase`. This anchors the comparison to the
+    whole path rather than the right-hand side of it, so a bare entry
+    like ``"README.md"`` matches only the project-root README and not
+    nested READMEs like ``evals/README.md``. See issue #47.
+
+    Note that fnmatch's ``*`` is greedy and matches across path
+    separators — for our never-patch use case that loosens existing
+    patterns slightly (e.g. ``src/tools/*.py`` now also matches
+    ``src/tools/sub/foo.py``). This is safer for never-patch since
+    the goal is to keep the user's code off-limits; over-matching
+    here protects more, not less.
+    """
     file_str = str(file_path)
-    for pattern in never_patch:
-        if Path(file_str).match(pattern):
-            return True
-    return False
+    return any(fnmatch.fnmatchcase(file_str, pattern) for pattern in never_patch)
 
 
 def _show_diff_and_ask(

tests/test_patch.py

@@ -165,6 +165,95 @@ def test_user_directory_is_never_patched(self, expected):
         assert expected in AGENT_NEVER_PATCH
 
 
+class TestShouldNeverPatch:
+    """Issue #47: bare patterns like "README.md" used to match nested
+    files (evals/README.md, docs/foo/README.md) because Path.match
+    matches from the right. The matcher now anchors to the full path
+    via fnmatch.fnmatchcase.
+    """
+
+    @pytest.mark.parametrize(
+        "rel_path,expected",
+        [
+            # The bug from #47 — bare README.md must NOT lock out nested ones
+            ("evals/README.md", False),
+            ("docs/sub/README.md", False),
+            # The project-root README.md must still be protected
+            ("README.md", True),
+            # Negative: a non-README file is unaffected
+            ("evals/discovery.py", False),
+        ],
+    )
+    def test_bare_filename_matches_only_root(self, rel_path, expected):
+        # Minimal never_patch list — just the bare filename
+        assert patching._should_never_patch(Path(rel_path), ["README.md"]) is expected
+
+    @pytest.mark.parametrize(
+        "rel_path,expected",
+        [
+            ("agent.yaml", True),
+            ("not-agent.yaml", False),
+            ("chart/values.yaml", True),
+            ("chart/templates/values.yaml", False),
+            ("src/agent.py", True),
+            ("src/agents.py", False),
+        ],
+    )
+    def test_exact_path_patterns(self, rel_path, expected):
+        patterns = ["agent.yaml", "chart/values.yaml", "src/agent.py"]
+        assert patching._should_never_patch(Path(rel_path), patterns) is expected
+
+    @pytest.mark.parametrize(
+        "rel_path,expected",
+        [
+            ("src/fipsagents/foo.py", True),
+            ("src/fipsagents/sub/foo.py", True),
+            ("src/fipsagents/sub/deeper/foo.py", True),
+            ("src/other/foo.py", False),
+        ],
+    )
+    def test_recursive_glob(self, rel_path, expected):
+        assert patching._should_never_patch(Path(rel_path), ["src/fipsagents/**"]) is expected
+
+    @pytest.mark.parametrize(
+        "rel_path,expected",
+        [
+            # tests/**/*.py requires at least one nested directory
+            ("tests/foo/bar.py", True),
+            ("tests/foo/bar/baz.py", True),
+            ("tests/foo.py", False),  # No nested dir
+            ("other/foo.py", False),
+        ],
+    )
+    def test_tests_recursive_pattern(self, rel_path, expected):
+        assert patching._should_never_patch(Path(rel_path), ["tests/**/*.py"]) is expected
+
+    @pytest.mark.parametrize(
+        "rel_path,expected",
+        [
+            (".env", True),
+            (".env.local", True),
+            (".env.production", True),
+            ("env", False),
+            ("not-.env", False),
+        ],
+    )
+    def test_dotenv_glob(self, rel_path, expected):
+        assert patching._should_never_patch(Path(rel_path), [".env*"]) is expected
+
+    def test_empty_pattern_list_never_matches(self):
+        assert patching._should_never_patch(Path("anything.py"), []) is False
+
+    def test_real_never_patch_lists_protect_root_readme_only(self):
+        # Regression: the actual constants must not lock out evals/README.md
+        # (which the agent template ships as part of the eval harness).
+        assert patching._should_never_patch(Path("README.md"), AGENT_NEVER_PATCH) is True
+        assert patching._should_never_patch(Path("evals/README.md"), AGENT_NEVER_PATCH) is False
+        # Same expectation for the MCP list
+        assert patching._should_never_patch(Path("README.md"), MCP_NEVER_PATCH) is True
+        assert patching._should_never_patch(Path("docs/README.md"), MCP_NEVER_PATCH) is False
+
+
 # ---------------------------------------------------------------------------
 # Unit tests — find_fips_project_root walks up to .template-info
 # ---------------------------------------------------------------------------