fix(tests): make git test wrappers exec the real git binary

tests/agents/hooks/test_cleanup_worktrees.py

@@ -3,13 +3,13 @@
 import json
 from pathlib import Path
 import shlex
-import shutil
 import subprocess
 import sys
 
 import pytest
 
 from tests.agents.hooks.cleanup_worktrees_runtime import SCRIPT, branches, cleanup, git, task_worktree
+from tests.runtime import real_git
 
 import herdr_ownership
 import session_store
@@ -26,8 +26,7 @@ def test_a_merged_clean_worktree_and_its_branch_are_removed(primary: Path, merge
 def test_removal_does_not_repeat_gits_cleanliness_check(primary: Path, merged: dict[str, str], tmp_path: Path) -> None:
     path = task_worktree(primary, "feat/done")
     merged["feat/done"] = git("rev-parse", "HEAD", cwd=path)
-    executable = shutil.which("git")
-    assert executable
+    executable = real_git()
     wrapper = tmp_path / "bin/git"
     wrapper.write_text(
         '#!/bin/sh\ncase " $* " in *" worktree remove "*)\n'

tests/agents/hooks/test_cleanup_worktrees_isolation.py

@@ -9,6 +9,7 @@
 import pytest_mock
 
 from tests.agents.hooks.cleanup_worktrees_runtime import branches, cleanup, git, task_worktree
+from tests.runtime import real_git
 
 import cleanup_worktrees
 
@@ -37,8 +38,7 @@ def test_lane_status_never_runs_a_filter_from_raced_admin_configuration(
     readme.write_text("base\n")
     index_time = (admin / "index").stat().st_mtime_ns
     os.utime(readme, ns=(index_time, index_time))
-    executable = shutil.which("git")
-    assert executable
+    executable = real_git()
     rewrite = ""
     if planted in {"commondir", "both"}:
         rewrite += f"printf '%s' {shlex.quote(str(fake))} > {shlex.quote(str(admin / 'commondir'))}\n"
@@ -241,12 +241,10 @@ def test_lane_fsmonitor_is_never_executed_and_git_and_gh_run_from_the_primary(
     git("config", *(["--worktree"] if config == "worktree" else []), "core.fsmonitor", str(monitor), cwd=path)
     discovery = tmp_path / "lane-discovery"
     for name in ("git", "gh"):
-        executable = shutil.which(name)
-        assert executable
+        executable = real_git() if name == "git" else str(tmp_path / "original-gh")
         wrapper = tmp_path / "bin" / name
         if name == "gh":
             wrapper.rename(tmp_path / "original-gh")
-            executable = str(tmp_path / "original-gh")
         wrapper.write_text(
             f'#!/bin/sh\ncase "$PWD" in {shlex.quote(str(path))}*|{shlex.quote(str(current))}*) '
             f'touch {shlex.quote(str(discovery))}; exit 99;; esac\nexec {shlex.quote(executable)} "$@"\n'
@@ -298,8 +296,7 @@ def test_a_planted_git_entry_inside_a_lane_is_neither_current_nor_primary(
         git("init", "--quiet", cwd=nested)
     monkeypatch.setenv("HOME", str(home))
     marker = tmp_path / "nested-git-ran"
-    executable = shutil.which("git")
-    assert executable
+    executable = real_git()
     wrapper = tmp_path / "bin/git"
     wrapper.write_text(
         f'#!/bin/sh\nif [ "$PWD" = {shlex.quote(str(nested))} ]; then '

tests/agents/hooks/test_cleanup_worktrees_trust.py

@@ -4,7 +4,6 @@
 import os
 from pathlib import Path
 import shlex
-import shutil
 import tempfile
 from collections.abc import Iterator
 
@@ -17,6 +16,7 @@
     git,
     task_worktree,
 )
+from tests.runtime import real_git
 
 import cleanup_worktrees
 
@@ -55,13 +55,11 @@ def herdr_lane(primary: Path) -> Path:
 def record_commands(tmp_path: Path, forbidden: Path) -> Path:
     marker = tmp_path / "untrusted-command"
     for name in ("git", "gh"):
-        executable = shutil.which(name)
-        assert executable
+        executable = real_git() if name == "git" else str(tmp_path / "original-gh")
         wrapper = tmp_path / "bin" / name
         if name == "gh":
             original = tmp_path / "original-gh"
             wrapper.rename(original)
-            executable = str(original)
         wrapper.write_text(
             f'#!/bin/sh\nprintf "%s %s %s\\n" "$PWD" {name} "$*" >> {shlex.quote(str(tmp_path / "commands"))}\n'
             f'case "$PWD $*" in *{shlex.quote(str(forbidden))}*) '
@@ -210,8 +208,7 @@ def test_git_removal_is_isolated_and_herdr_only_closes_the_workspace(
     lane = task_worktree(primary, "feat/done")
     worktree = next(tree for tree in cleanup_worktrees.linked_worktrees(primary) if tree.path == lane)
     # The process wrapper rejects any invocation missing the required isolation.
-    executable = shutil.which("git")
-    assert executable
+    executable = real_git()
     wrapper = tmp_path / "bin/git"
     wrapper.write_text(
         '#!/bin/sh\ncase " $* " in *" worktree remove "*)\n'

tests/runtime.py

@@ -13,6 +13,15 @@
 StubWriter = Callable[[str, str], Path]
 
 
+def real_git() -> str:
+    """Resolve Git before installing a PATH wrapper that delegates to it."""
+    result = subprocess.run(["git", "--exec-path"], check=True, capture_output=True, text=True, timeout=10)
+    # /usr/bin/git on macOS redispatches through PATH; git-core/git is the actual binary.
+    executable = (Path(result.stdout.strip()) / "git").resolve()
+    assert executable.is_file()
+    return str(executable)
+
+
 def load_script_module(relative_path: str, module_name: str) -> ModuleType:
     """Load a trusted repository module for direct behavior tests."""
     spec = util.spec_from_file_location(module_name, REPO_ROOT / relative_path)

tests/test_git_wrapper.py

@@ -0,0 +1,41 @@
+"""Git wrappers delegate without re-entering PATH-based platform shims."""
+
+import os
+from pathlib import Path
+import shlex
+import subprocess
+
+import pytest
+
+from tests.runtime import real_git
+
+
+@pytest.mark.parametrize("shim_first", [True, False])
+def test_git_wrapper_bypasses_path_lookup_in_platform_shims(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, shim_first: bool
+) -> None:
+    exec_path = subprocess.run(["git", "--exec-path"], check=True, capture_output=True, text=True).stdout.strip()
+    binary = Path(exec_path) / "git"
+    expected = subprocess.run([str(binary), "--version"], check=True, capture_output=True, text=True).stdout
+    shim = tmp_path / "shim"
+    shim.mkdir()
+    (shim / "git").write_text(
+        '#!/bin/sh\nif [ "$1" = --exec-path ]; then\n'
+        f"printf '%s\\n' {shlex.quote(exec_path)}\n"
+        'else\nexec git "$@"\nfi\n'
+    )
+    (shim / "git").chmod(0o755)
+    directories = [str(shim), str(binary.parent)]
+    if not shim_first:
+        directories.reverse()
+    monkeypatch.setenv("PATH", os.pathsep.join(directories))
+    executable = real_git()
+    wrapper = tmp_path / "wrapper"
+    wrapper.mkdir()
+    (wrapper / "git").write_text(f'#!/bin/sh\nexec {shlex.quote(executable)} "$@"\n')
+    (wrapper / "git").chmod(0o755)
+    monkeypatch.setenv("PATH", str(wrapper) + os.pathsep + os.environ["PATH"])
+
+    result = subprocess.run(["git", "--version"], check=True, capture_output=True, text=True, timeout=30)
+
+    assert result.stdout == expected