Test .gitignore with */* is applied correctly

The test contains two cases: when the .gitignore with the special rule
to ignore every subfolder and its contents (*/*) is in the root, and
when the file is inside a subfolder relative to root (nested). In both
cases, we compare the files that are visible by Black with a known
list of paths containing the expected values.

Before the fix introduced in the previous commit, this test failed when
the .gitignore file was nested (second case). Now, the test is passed
for both cases.

Signed-off-by: Antonio Ossa Guerra <aaossa@uc.cl>

tests/data/ignore_subfolders_gitignore_tests/subdir/.gitignore

@@ -0,0 +1 @@
+*/*

tests/test_black.py

@@ -2056,6 +2056,24 @@ def test_invalid_nested_gitignore(self) -> None:
         gitignore = path / "a" / ".gitignore"
         assert f"Could not parse {gitignore}" in result.stderr_bytes.decode()
 
+    def test_gitignore_that_ignores_subfolders(self) -> None:
+        # If gitignore with */* is in root
+        root = Path(DATA_DIR / "ignore_subfolders_gitignore_tests" / "subdir")
+        expected = [root / "b.py"]
+        ctx = FakeContext()
+        ctx.obj["root"] = root
+        assert_collected_sources([root], expected, ctx=ctx)
+
+        # If .gitignore with */* is nested
+        root = Path(DATA_DIR / "ignore_subfolders_gitignore_tests")
+        expected = [
+            root / "a.py",
+            root / "subdir" / "b.py",
+        ]
+        ctx = FakeContext()
+        ctx.obj["root"] = root
+        assert_collected_sources([root], expected, ctx=ctx)
+
     def test_empty_include(self) -> None:
         path = DATA_DIR / "include_exclude_tests"
         src = [path]