Use .gitignore files in the initial source directories (#3237)

Solves #2598 where Black wouldn't
use .gitignore at folder/.gitignore if you ran `black folder` for
example.

Co-authored-by: Richard Si <63936253+ichard26@users.noreply.github.com>

CHANGES.md

@@ -44,6 +44,9 @@
 - Black now uses the presence of debug f-strings to detect target version. (#3215)
 - Fix misdetection of project root and verbose logging of sources in cases involving
   `--stdin-filename` (#3216)
+- Immediate `.gitignore` files in source directories given on the command line are now
+  also respected, previously only `.gitignore` files in the project root and
+  automatically discovered directories were respected (#3237)
 
 ### Documentation
 

src/black/__init__.py

@@ -653,6 +653,11 @@ def get_sources(
             if exclude is None:
                 exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES)
                 gitignore = get_gitignore(root)
+                p_gitignore = get_gitignore(p)
+                # No need to use p's gitignore if it is identical to root's gitignore
+                # (i.e. root and p point to the same directory).
+                if gitignore != p_gitignore:
+                    gitignore += p_gitignore
             else:
                 gitignore = None
             sources.update(

tests/test_black.py

@@ -1990,6 +1990,13 @@ def test_nested_gitignore(self) -> None:
         )
         assert sorted(expected) == sorted(sources)
 
+    def test_nested_gitignore_directly_in_source_directory(self) -> None:
+        # https://github.com/psf/black/issues/2598
+        path = Path(DATA_DIR / "nested_gitignore_tests")
+        src = Path(path / "root" / "child")
+        expected = [src / "a.py", src / "c.py"]
+        assert_collected_sources([src], expected)
+
     def test_invalid_gitignore(self) -> None:
         path = THIS_DIR / "data" / "invalid_gitignore_tests"
         empty_config = path / "pyproject.toml"