Finish making TestCygpath xfail markings granular

This marks only the (many, but not all) really expected failure
cases in test_cygpath_ok as xfail, preventing the others from
giving "XPASS" results each time the tests are run.

This finishes making the xfail markings in TestCygpath granular, in
the sense that now there should be no "XPASS" results. However, the
approach taken here might still benefit from future reorganization
or refactoring.

Author: EliahKagan

Diff for: test/test_util.py

@@ -216,37 +216,59 @@ def _xfail_param(*values, **xfail_kwargs):
     return pytest.param(*values, marks=pytest.mark.xfail(**xfail_kwargs))
 
 
-@pytest.mark.skipif(sys.platform != "cygwin", reason="Paths specifically for Cygwin.")
-class TestCygpath:
-    """Tests for :func:`git.util.cygpath` and :func:`git.util.decygpath`."""
+_norm_cygpath_pairs = (
+    (R"foo\bar", "foo/bar"),
+    (R"foo/bar", "foo/bar"),
+    (R"C:\Users", "/cygdrive/c/Users"),
+    (R"C:\d/e", "/cygdrive/c/d/e"),
+    ("C:\\", "/cygdrive/c/"),
+    (R"\\server\C$\Users", "//server/C$/Users"),
+    (R"\\server\C$", "//server/C$"),
+    ("\\\\server\\c$\\", "//server/c$/"),
+    (R"\\server\BAR/", "//server/BAR/"),
+    (R"D:/Apps", "/cygdrive/d/Apps"),
+    (R"D:/Apps\fOO", "/cygdrive/d/Apps/fOO"),
+    (R"D:\Apps/123", "/cygdrive/d/Apps/123"),
+)
 
-    _norm_cygpath_pairs = (
-        (R"foo\bar", "foo/bar"),
-        (R"foo/bar", "foo/bar"),
-        (R"C:\Users", "/cygdrive/c/Users"),
-        (R"C:\d/e", "/cygdrive/c/d/e"),
-        ("C:\\", "/cygdrive/c/"),
-        (R"\\server\C$\Users", "//server/C$/Users"),
-        (R"\\server\C$", "//server/C$"),
-        ("\\\\server\\c$\\", "//server/c$/"),
-        (R"\\server\BAR/", "//server/BAR/"),
-        (R"D:/Apps", "/cygdrive/d/Apps"),
-        (R"D:/Apps\fOO", "/cygdrive/d/Apps/fOO"),
-        (R"D:\Apps/123", "/cygdrive/d/Apps/123"),
-    )
+_unc_cygpath_pairs = (
+    (R"\\?\a:\com", "/cygdrive/a/com"),
+    (R"\\?\a:/com", "/cygdrive/a/com"),
+    (R"\\?\UNC\server\D$\Apps", "//server/D$/Apps"),
+)
 
-    _unc_cygpath_pairs = (
-        (R"\\?\a:\com", "/cygdrive/a/com"),
-        (R"\\?\a:/com", "/cygdrive/a/com"),
-        (R"\\?\UNC\server\D$\Apps", "//server/D$/Apps"),
+# Mapping of expected failures for the test_cygpath_ok test.
+_cygpath_ok_xfails = {
+    # From _norm_cygpath_pairs:
+    (R"C:\Users", "/cygdrive/c/Users"): "/proc/cygdrive/c/Users",
+    (R"C:\d/e", "/cygdrive/c/d/e"): "/proc/cygdrive/c/d/e",
+    ("C:\\", "/cygdrive/c/"): "/proc/cygdrive/c/",
+    (R"\\server\BAR/", "//server/BAR/"): "//server/BAR",
+    (R"D:/Apps", "/cygdrive/d/Apps"): "/proc/cygdrive/d/Apps",
+    (R"D:/Apps\fOO", "/cygdrive/d/Apps/fOO"): "/proc/cygdrive/d/Apps/fOO",
+    (R"D:\Apps/123", "/cygdrive/d/Apps/123"): "/proc/cygdrive/d/Apps/123",
+    # From _unc_cygpath_pairs:
+    (R"\\?\a:\com", "/cygdrive/a/com"): "/proc/cygdrive/a/com",
+    (R"\\?\a:/com", "/cygdrive/a/com"): "/proc/cygdrive/a/com",
+}
+
+
+# Parameter sets for the test_cygpath_ok test.
+_cygpath_ok_params = [
+    (
+        _xfail_param(*case, reason=f"Returns: {_cygpath_ok_xfails[case]!r}", raises=AssertionError)
+        if case in _cygpath_ok_xfails
+        else case
     )
+    for case in _norm_cygpath_pairs + _unc_cygpath_pairs
+]
 
-    # FIXME: Mark only the /proc-prefixing cases xfail (or fix them).
-    @pytest.mark.xfail(
-        reason="Many return paths prefixed /proc/cygdrive instead.",
-        raises=AssertionError,
-    )
-    @pytest.mark.parametrize("wpath, cpath", _norm_cygpath_pairs + _unc_cygpath_pairs)
+
+@pytest.mark.skipif(sys.platform != "cygwin", reason="Paths specifically for Cygwin.")
+class TestCygpath:
+    """Tests for :func:`git.util.cygpath` and :func:`git.util.decygpath`."""
+
+    @pytest.mark.parametrize("wpath, cpath", _cygpath_ok_params)
     def test_cygpath_ok(self, wpath, cpath):
         cwpath = cygpath(wpath)
         assert cwpath == cpath, wpath
@@ -255,7 +277,7 @@ def test_cygpath_ok(self, wpath, cpath):
         "wpath, cpath",
         [
             (R"./bar", "bar"),
-            _xfail_param(R".\bar", "bar", reason=R'Returns: "./bar"', raises=AssertionError),
+            _xfail_param(R".\bar", "bar", reason="Returns: './bar'", raises=AssertionError),
             (R"../bar", "../bar"),
             (R"..\bar", "../bar"),
             (R"../bar/.\foo/../chu", "../bar/chu"),