test(gix): keep hook lookup and execution on Git

GixPython 0.1.0 exposes no hook lookup or execution API. The previous fast path
read configuration through Gix but used Python `os.stat()` to declare an absent
hook successful, so it was not a Gix implementation. Retain the existing CLI
path for every requested hook and document the required native binding as
`GIX-23`.

The missing-hook probe now deliberately retains one CLI launch per invocation
(zero reduction), replacing the former zero-call Python shortcut. Tests assert
six actual calls for three absent hooks across ordinary and linked worktrees,
retain pre-dispatch NUL rejection, and check existing/configured hook fallback.
The native handler and its special `GIT_EDITOR` config permission are removed.

Validation: Gix index, backend and safety tests passed first (236 passed,
2 skipped in 34.38s), then CLI (166 passed, 3 skipped in 28.61s). Ruff
lint/format and `git diff --check` passed. Native mutation failures continue
to be protected from CLI retries by the existing dispatch contract.

Author: codex

doc/gix-backend.md

@@ -143,6 +143,7 @@ The historical full-suite counts above predate this correction. A constant
 | Reference enumeration, `for_each_ref` | Sorted reference names and literal prefixes, preserving symbolic aliases | Dangling symbolic refs, root refs, glob patterns, other formats/options |
 | Managed `config --get KEY` | Merged repository config snapshot | Files/streams, enumeration, mutation; GIX-12 |
 | Submodule enumeration and cached fields | Dedicated native `.gitmodules` parser over the existing worktree/blob source, with raw path/URL/branch values | Other/duplicate sections, ambiguous brackets, missing/implicit fields and parser errors; GIX-12 |
+| Commit hooks | No bound native lookup/execution API | All hooks, including absent hooks; GIX-23 |
 | Worktree inventory, `worktree list` | Main and linked worktree metadata, including bare main repositories and locks | Prunable entries; GIX-14 |
 | `Repo.merge_base`, `Repo.is_ancestor` | Native graph queries for two revisions | Octopus/fork-point and other options |
 | `Commit.count` | Reachable commit count, skip/limit/first-parent | Path filters and other revision options |
@@ -452,6 +453,7 @@ below use the supplied `pygix` source and its pinned Gitoxide revision.
 | GIX-20 | `Target.Symbolic(name)` validates full names but rejects standalone names accepted by `git check-ref-format --allow-onelevel`. Four of 430 audited calls differed: `refs` twice, `hellothere`, and `valid_one_level_refname`. Further probes include digits, punctuation and Unicode (`1`, `A1`, `HEAD_1`, `A-B`, `A.B`, `Ä`). | Expose Git-compatible partial/one-level name validation, or correct the native restriction where appropriate. This is a binding/behavior shortcoming to revisit upstream; standalone names rejected natively retain CLI validation. |
 | GIX-21 | Native snapshot overrides for `committer.name`, `committer.email` and `gitoxide.commit.committerDate` resolve correctly. Applying them to the retained repository would expose command-specific identity to other threads. GixPython 0.1.0 has no general independent repository clone: Python `copy`/`deepcopy` fail, while the binding's internal `RepoHandle::clone()` shares its `Arc` state. | Bind a cheap independent native clone with isolated config so native identity resolution can apply per-command overrides, including removal semantics. Reopening isolates state but repeats setup; `with_object_memory()` also changes object-write behavior and is not a general clone API. Keep native process/config identity and CLI for differing command overrides. Do not mutate process environment/shared snapshots or resolve identity fields in Python. Explicit canonical commit inputs may still be adapted to `gix.Signature`. |
 | GIX-22 | The native Git directory is sufficient for the two fixed metadata leaves used here: `modules` and `COMMIT_EDITMSG`. Git's `path.c` applies no special relocation to either, including in linked worktrees. The adapter appends only these names to the canonical native Git directory. | No new binding is needed for these ordinary paths. Other `--git-path` names and symlinked metadata leaves retain CLI resolution; a general resolver must handle config/environment overrides, common/private storage and canonical targets. `Repository.modules_path()` means `.gitmodules`, not the `modules` storage directory. |
+| GIX-23 | No hook lookup or execution API is bound in GixPython 0.1.0. The removed absence fast path read config through Gix but used Python `os.stat()` to declare success. | Bind native hook lookup with configured/default path, linked-worktree, missing/nonexecutable-hook and diagnostic semantics, plus execution where needed. Until then all managed hook calls use Git, including `--ignore-missing` no-ops. A Python filesystem check is not a Gix implementation. |
 
 For GIX-8, at fixture commit `44e0a8ec55c42559dfcdf5117710b26261a7c937`,
 compare `git rev-list HEAD` with
@@ -512,7 +514,7 @@ this investigation; this item does not claim a process reduction.
 | Object enumeration and alternate-directory listing | No binding for complete ODB object iteration or alternate-store enumeration; `cat-file --batch-all-objects` / `count-objects` remain. |
 | Name-rev, trailer parsing, cherry | No equivalent bound operation. Native describe is not name-rev. |
 | Config-backed remote/submodule maintenance | Missing config enumeration/multivar/removal operations (GIX-12), plus filesystem and worktree lifecycle requirements. |
-| Hook execution | Explicitly requested hooks retain the existing Git-managed behavior. Native operations retain GitPython's default hook/fsmonitor/maintenance restrictions. |
+| Hook execution | Every explicit hook request, including an absent hook, retains Git-managed lookup, execution and diagnostics until GIX-23 is addressed. Native operations retain GitPython's default hook/fsmonitor/maintenance restrictions. |
 
 ## Maintaining the adapters
 

test/test_gix_backend.py

@@ -11,7 +11,8 @@
 import pytest
 
 from git import Actor, Commit, Git, Reference, Repo, SymbolicReference, _backend
-from git.exc import GitCommandError, InvalidGitRepositoryError
+from git.exc import GitCommandError, InvalidGitRepositoryError, UnsafeOptionError
+from git.index.fun import run_commit_hook
 from git.index.typ import BaseIndexEntry
 from git.repo.fun import find_submodule_git_dir, find_worktree_git_dir, is_git_dir
 from gitdb import IStream
@@ -308,6 +309,33 @@ def test_native_tree_and_commit_bytes_match_cli(repo):
         assert commit.replace(message="a changed message").hexsha == native.hexsha
 
 
+def test_hooks_retain_cli_even_when_missing(repo, tmp_path):
+    repo.index.commit("initial", skip_hooks=True)
+    linked_path = tmp_path / "linked"
+    repo.git.worktree("add", "--detach", str(linked_path))
+    with Repo(linked_path) as linked:
+        linked.git.version_info
+        count = _backend.statistics().get(("Git.execute", "CLI process"), 0)
+        with patch.object(Git, "execute", autospec=True, side_effect=Git.execute) as cli:
+            for current in (repo, linked):
+                for name in ("pre-commit", "commit-msg", "post-commit"):
+                    run_commit_hook(name, current.index)
+            with pytest.raises(UnsafeOptionError, match="NUL"):
+                run_commit_hook("commit-msg", repo.index, "message\0path")
+            assert cli.call_count == 6
+        assert _backend.statistics().get(("Git.execute", "CLI process"), 0) == count + 6
+        hook = Path(repo.common_dir, "hooks", "pre-commit")
+        hook.parent.mkdir(exist_ok=True)
+        hook.write_text("present, even without executable permission")
+        with patch.object(Git, "execute", return_value="") as cli:
+            run_commit_hook("pre-commit", linked.index)
+            cli.assert_called_once()
+        repo.git.config("core.hooksPath", "custom-hooks")
+        with patch.object(Git, "execute", return_value="") as cli:
+            run_commit_hook("post-commit", repo.index)
+            cli.assert_called_once()
+
+
 def test_native_submodule_inventory_and_cached_fields_match_cli(repo):
     first = repo.index.commit("initial", skip_hooks=True)
     config = Path(repo.working_dir, ".gitmodules")