core.git: add get_repo_root query and use it in repository scaffold

https://chatgpt.com/share/69414f70-fc60-800f-ba6a-cbea426ea913

src/pkgmgr/actions/repository/scaffold.py

@@ -1,10 +1,12 @@
+# src/pkgmgr/actions/repository/scaffold.py
 from __future__ import annotations
 
 import os
-import subprocess
 from pathlib import Path
 from typing import Any, Dict, Optional
 
+from pkgmgr.core.git.queries import get_repo_root
+
 try:
     from jinja2 import Environment, FileSystemLoader, StrictUndefined
 except Exception as exc:  # pragma: no cover
@@ -22,20 +24,10 @@ def _repo_root_from_here(anchor: Optional[Path] = None) -> str:
     Fallback to a conservative relative parent lookup.
     """
     here = (anchor or Path(__file__)).resolve().parent
-    try:
-        r = subprocess.run(
-            ["git", "rev-parse", "--show-toplevel"],
-            cwd=str(here),
-            check=False,
-            capture_output=True,
-            text=True,
-        )
-        if r.returncode == 0:
-            top = (r.stdout or "").strip()
-            if top:
-                return top
-    except Exception:
-        pass
+
+    top = get_repo_root(cwd=str(here))
+    if top:
+        return top
 
     # Fallback: src/pkgmgr/actions/repository/scaffold.py -> <repo root> = parents[5]
     p = (anchor or Path(__file__)).resolve()

src/pkgmgr/core/git/queries/__init__.py

@@ -13,6 +13,7 @@ from .get_tags_at_ref import get_tags_at_ref, GitTagsAtRefQueryError
 from .get_config_value import get_config_value
 from .get_upstream_ref import get_upstream_ref
 from .list_tags import list_tags
+from .get_repo_root import get_repo_root
 
 __all__ = [
     "get_current_branch",
@@ -31,4 +32,5 @@ __all__ = [
     "get_config_value",
     "get_upstream_ref",
     "list_tags",
+    "get_repo_root",
 ]

src/pkgmgr/core/git/queries/get_repo_root.py

@@ -0,0 +1,23 @@
+# src/pkgmgr/core/git/queries/get_repo_root.py
+from __future__ import annotations
+
+from typing import Optional
+
+from ..errors import GitError
+from ..run import run
+
+
+def get_repo_root(*, cwd: str = ".") -> Optional[str]:
+    """
+    Return the git repository root directory (top-level), or None if not available.
+
+    Equivalent to:
+      git rev-parse --show-toplevel
+    """
+    try:
+        out = run(["rev-parse", "--show-toplevel"], cwd=cwd)
+    except GitError:
+        return None
+
+    out = out.strip()
+    return out or None