gitpython-developers
diff --git a/‎git/index/fun.py‎
Lines changed: 8 additions & 2 deletions b/‎git/index/fun.py‎
Lines changed: 8 additions & 2 deletions
diff --git a/‎test/test_index.py‎
Lines changed: 17 additions & 0 deletions b/‎test/test_index.py‎
Lines changed: 17 additions & 0 deletions
@@ -104,8 +104,14 @@ def run_commit_hook(name: str, index: "IndexFile", *args: str) -> None:
         if sys.platform == "win32" and not _has_file_extension(hp):
             # Windows only uses extensions to determine how to open files
             # (doesn't understand shebangs). Try using bash to run the hook.
-            relative_hp = Path(hp).relative_to(index.repo.working_dir).as_posix()
-            cmd = ["bash.exe", relative_hp]
+            try:
+                bash_hp = osp.relpath(hp, index.repo.working_dir)
+            except ValueError:
+                # Different drives have no relative path on Windows. Git Bash accepts
+                # an absolute path in this form, although a relative path is preferable
+                # because it also works with the Windows Subsystem for Linux wrapper.
+                bash_hp = hp
+            cmd = ["bash.exe", Path(bash_hp).as_posix()]
 
         process = safer_popen(
             cmd + list(args),
 
@@ -1104,6 +1104,23 @@ def test_run_commit_hook(self, rw_repo):
         output = Path(rw_repo.git_dir, "output.txt").read_text(encoding="utf-8")
         self.assertEqual(output, "ran fake hook\n")
 
+    @with_rw_directory
+    def test_run_commit_hook_outside_worktree_on_windows(self, rw_dir):
+        root = Path(rw_dir).resolve()
+        repo = Repo.init(root / "repo")
+        hooks_dir = root / "hooks"
+        _make_hook(root, "fake-hook", "exit 0")
+        with repo.config_writer() as writer:
+            writer.set_value("core", "hooksPath", str(hooks_dir))
+
+        with mock.patch("git.index.fun.sys.platform", "win32"):
+            with mock.patch("git.index.fun.safer_popen") as popen, mock.patch("git.index.fun.handle_process_output"):
+                popen.return_value.returncode = 0
+                run_commit_hook("fake-hook", repo.index)
+
+        command = popen.call_args.args[0]
+        self.assertEqual(command, ["bash.exe", "../hooks/fake-hook"])
+
     @ddt.data((False,), (True,))
     @with_rw_directory
     def test_hook_uses_shell_not_from_cwd(self, rw_dir, case):