Add xfail marks to hook tests for WinBashStatus.Absent

Precise xfail marks were added to commit hook tests in #1745, but
in a few tests I didn't get it right for WinBashStatus.Absent. That
is, on a Windows system that has no bash.exe at all:

- More of the tests are unable to pass than have xfail marks.

- One of the tests, test_commit_msg_hook_success, which does have
  an xfail mark for that, wrongly combines it with the xfail mark
  for WinBashStatus.Wsl. That test is the only one where the WSL
  bash.exe, even when a working WSL distribution is installed, is
  unable to pass. But using a single mark there is wrong, in part
  because the "reason" is not correct for both, but even more so
  because the exceptions they raise are different: AssertionError
  is raised when the WSL bash.exe is used in that test, but when
  bash.exe is altogether absent, HookExecutionError is raised.

This fixes that by adding xfail marks for WinBashStatus.Absent
where missing, and splitting test_commit_msg_hook_success's xfail
mark that unsuccessfully tried to cover two conditions into two
separate marks, each of which gives a correct reason and exception.

This commit also rewords the xfail reason given for WslNoDistro,
which was somewhat unclear and potentially ambiguous, to make it
clearer.

Author: EliahKagan

Diff for: test/test_index.py

@@ -991,9 +991,14 @@ class Mocked:
         rel = index._to_relative_path(path)
         self.assertEqual(rel, os.path.relpath(path, root))
 
+    @pytest.mark.xfail(
+        type(_win_bash_status) is WinBashStatus.Absent,
+        reason="Can't run a hook on Windows without bash.exe.",
+        rasies=HookExecutionError,
+    )
     @pytest.mark.xfail(
         type(_win_bash_status) is WinBashStatus.WslNoDistro,
-        reason="Currently uses the bash.exe for WSL even with no WSL distro installed",
+        reason="Currently uses the bash.exe of WSL, even with no WSL distro installed",
         raises=HookExecutionError,
     )
     @with_rw_repo("HEAD", bare=True)
@@ -1004,7 +1009,7 @@ def test_pre_commit_hook_success(self, rw_repo):
 
     @pytest.mark.xfail(
         type(_win_bash_status) is WinBashStatus.WslNoDistro,
-        reason="Currently uses the bash.exe for WSL even with no WSL distro installed",
+        reason="Currently uses the bash.exe of WSL, even with no WSL distro installed",
         raises=AssertionError,
     )
     @with_rw_repo("HEAD", bare=True)
@@ -1030,13 +1035,18 @@ def test_pre_commit_hook_fail(self, rw_repo):
             raise AssertionError("Should have caught a HookExecutionError")
 
     @pytest.mark.xfail(
-        type(_win_bash_status) in {WinBashStatus.Absent, WinBashStatus.Wsl},
+        type(_win_bash_status) is WinBashStatus.Absent,
+        reason="Can't run a hook on Windows without bash.exe.",
+        rasies=HookExecutionError,
+    )
+    @pytest.mark.xfail(
+        type(_win_bash_status) is WinBashStatus.Wsl,
         reason="Specifically seems to fail on WSL bash (in spite of #1399)",
         raises=AssertionError,
     )
     @pytest.mark.xfail(
         type(_win_bash_status) is WinBashStatus.WslNoDistro,
-        reason="Currently uses the bash.exe for WSL even with no WSL distro installed",
+        reason="Currently uses the bash.exe of WSL, even with no WSL distro installed",
         raises=HookExecutionError,
     )
     @with_rw_repo("HEAD", bare=True)
@@ -1054,7 +1064,7 @@ def test_commit_msg_hook_success(self, rw_repo):
 
     @pytest.mark.xfail(
         type(_win_bash_status) is WinBashStatus.WslNoDistro,
-        reason="Currently uses the bash.exe for WSL even with no WSL distro installed",
+        reason="Currently uses the bash.exe of WSL, even with no WSL distro installed",
         raises=AssertionError,
     )
     @with_rw_repo("HEAD", bare=True)