Add check for illegal Widnows names

Fixes #589

tests/check_illegal_windows_names_test.py

@@ -0,0 +1,78 @@
+import sys
+
+import pytest
+
+from pre_commit_hooks.check_illegal_windows_names import (
+    find_illegal_windows_names,
+)
+from pre_commit_hooks.check_illegal_windows_names import main
+from pre_commit_hooks.check_illegal_windows_names import parents
+from pre_commit_hooks.util import cmd_output
+
+skip_win32 = pytest.mark.skipif(
+    sys.platform == 'win32',
+    reason='case conflicts between directories and files',
+)
+
+
+def test_parents():
+    assert set(parents('a')) == set()
+    assert set(parents('a/b')) == {'a'}
+    assert set(parents('a/b/c')) == {'a/b', 'a'}
+    assert set(parents('a/b/c/d')) == {'a/b/c', 'a/b', 'a'}
+
+
+def test_nothing_added(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        assert find_illegal_windows_names(['f.py']) == 0
+
+
+def test_adding_something(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        temp_git_dir.join('f.py').write("print('hello world')")
+        cmd_output('git', 'add', 'f.py')
+
+        assert find_illegal_windows_names(['f.py']) == 0
+
+
+@skip_win32  # pragma: win32 no cover
+def test_adding_something_with_illegal_filename(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        temp_git_dir.join('CoM3.py').write("print('hello world')")
+        cmd_output('git', 'add', 'CoM3.py')
+
+        assert find_illegal_windows_names(['CoM3.py']) == 1
+
+
+@skip_win32  # pragma: win32 no cover
+def test_adding_files_with_illegal_directory(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        temp_git_dir.mkdir('lpt2').join('x').write('foo')
+        cmd_output('git', 'add', '-A')
+
+        assert find_illegal_windows_names([]) == 1
+
+
+@skip_win32  # pragma: win32 no cover
+def test_adding_files_with_illegal_deep_directories(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        temp_git_dir.mkdir('x').mkdir('y').join('pRn').write('foo')
+        cmd_output('git', 'add', '-A')
+
+        assert find_illegal_windows_names([]) == 1
+
+
+@skip_win32  # pragma: win32 no cover
+def test_integration(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        assert main(argv=[]) == 0
+
+        temp_git_dir.join('f.py').write("print('hello world')")
+        cmd_output('git', 'add', 'f.py')
+
+        assert main(argv=['f.py']) == 0
+
+        temp_git_dir.join('CON.py').write("print('hello world')")
+        cmd_output('git', 'add', 'CON.py')
+
+        assert main(argv=['CON.py']) == 1