Fix: black only respects the root gitignore. (#2225)

Commit history before merge:

Black now respects .gitignore files in all levels, not only root/.gitignore file
(apply .gitignore rules like git does).

* Fix: typo
* Fix: respect .gitignore files in all levels.
* Add: CHANGELOG note.
* Fix: TypeError: unsupported operand type(s) for +: 'NoneType' and 'PathSpec'
* Update docs.
* Fix: no parent .gitignore
* Add a comment since the if expression is a bit hard to understand
* Update tests - conver no parent .gitignore case.
* Use main's Pipfile.lock instead

  The original changes in Pipfile.lock are whitespace only. The changes
  turned the JSON's file indentation from 4 to 2. Effectively this
  happened: `json.dumps(json.loads(old_pipfile_lock), indent=2) + "\n"`.

  Just using main's Pipfile.lock instead of undoing the changes because
  1) I don't know how to do that easily and quickly, and 2) there's a
  merge conflict.

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

* Merge remote-tracking branch 'upstream/main' into i1730 …
  
  conflicts for days ay?

CHANGES.md

@@ -4,6 +4,8 @@
 
 ### _Black_
 
+- Respect `.gitignore` files in all levels, not only `root/.gitignore` file (apply
+  `.gitignore` rules like `git` does) (#2225)
 - Restored compatibility with Click 8.0 on Python 3.6 when LANG=C used (#2227)
 
 ### _Blackd_

docs/usage_and_configuration/file_collection_and_discovery.md

@@ -30,8 +30,7 @@ then write the above files to `.cache/black/<version>/`.
 ## .gitignore
 
 If `--exclude` is not set, _Black_ will automatically ignore files and directories in
-`.gitignore` file, if present. The `.gitignore` file must be in the project root to be
-used and nested `.gitignore` aren't supported.
+`.gitignore` file(s), if present.
 
 If you want _Black_ to continue using `.gitignore` while also configuring the exclusion
 rules, please use `--extend-exclude`.

src/black/files.py

@@ -204,6 +204,8 @@ def gen_python_files(
             continue
 
         if child.is_dir():
+            # If gitignore is None, gitignore usage is disabled, while a Falsey
+            # gitignore is when the directory doesn't have a .gitignore file.
             yield from gen_python_files(
                 child.iterdir(),
                 root,
@@ -212,7 +214,7 @@ def gen_python_files(
                 extend_exclude,
                 force_exclude,
                 report,
-                gitignore,
+                gitignore + get_gitignore(child) if gitignore is not None else None,
             )
 
         elif child.is_file():

tests/data/nested_gitignore_tests/pyproject.toml

@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools>=41.0", "setuptools-scm", "wheel"]
+build-backend = "setuptools.build_meta"

tests/data/nested_gitignore_tests/root/.gitignore

@@ -0,0 +1 @@
+a.py

tests/data/nested_gitignore_tests/root/a.py

@@ -0,0 +1 @@
+# should be excluded (root/.gitignore)

tests/data/nested_gitignore_tests/root/b.py

@@ -0,0 +1 @@
+# should be included

tests/data/nested_gitignore_tests/root/c.py

@@ -0,0 +1 @@
+# should be included

tests/data/nested_gitignore_tests/root/child/.gitignore

@@ -0,0 +1 @@
+b.py

tests/data/nested_gitignore_tests/root/child/a.py

@@ -0,0 +1 @@
+# should be excluded (root/.gitignore)

tests/data/nested_gitignore_tests/root/child/b.py

@@ -0,0 +1 @@
+# should be excluded (child/.gitignore)

tests/data/nested_gitignore_tests/root/child/c.py

@@ -0,0 +1 @@
+# should be included

tests/test_black.py

@@ -1406,7 +1406,7 @@ def test_include_exclude(self) -> None:
         )
         self.assertEqual(sorted(expected), sorted(sources))
 
-    def test_gitingore_used_as_default(self) -> None:
+    def test_gitignore_used_as_default(self) -> None:
         path = Path(THIS_DIR / "data" / "include_exclude_tests")
         include = re.compile(r"\.pyi?$")
         extend_exclude = re.compile(r"/exclude/")
@@ -1703,6 +1703,33 @@ def test_gitignore_exclude(self) -> None:
         )
         self.assertEqual(sorted(expected), sorted(sources))
 
+    def test_nested_gitignore(self) -> None:
+        path = Path(THIS_DIR / "data" / "nested_gitignore_tests")
+        include = re.compile(r"\.pyi?$")
+        exclude = re.compile(r"")
+        root_gitignore = black.files.get_gitignore(path)
+        report = black.Report()
+        expected: List[Path] = [
+            Path(path / "x.py"),
+            Path(path / "root/b.py"),
+            Path(path / "root/c.py"),
+            Path(path / "root/child/c.py"),
+        ]
+        this_abs = THIS_DIR.resolve()
+        sources = list(
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                include,
+                exclude,
+                None,
+                None,
+                report,
+                root_gitignore,
+            )
+        )
+        self.assertEqual(sorted(expected), sorted(sources))
+
     def test_empty_include(self) -> None:
         path = THIS_DIR / "data" / "include_exclude_tests"
         report = black.Report()