nixos-rebuild-ng: remove explicit check for git and instead check exception

pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/nix.py

@@ -1,5 +1,4 @@
 import os
-import shutil
 from datetime import datetime
 from pathlib import Path
 from subprocess import PIPE, CalledProcessError
@@ -96,20 +95,19 @@ def get_nixpkgs_rev(nixpkgs_path: Path | None) -> str | None:
     if not nixpkgs_path:
         return None
 
-    # Git is not included in the closure for nixos-rebuild so we need to check
-    if not shutil.which("git"):
+    try:
+        # Get current revision
+        r = run_wrapper(
+            ["git", "-C", nixpkgs_path, "rev-parse", "--short", "HEAD"],
+            check=False,
+            stdout=PIPE,
+        )
+    except FileNotFoundError:
+        # Git is not included in the closure so we need to check
         info(f"warning: Git not found; cannot figure out revision of '{nixpkgs_path}'")
         return None
 
-    # Get current revision
-    r = run_wrapper(
-        ["git", "-C", nixpkgs_path, "rev-parse", "--short", "HEAD"],
-        check=False,
-        stdout=PIPE,
-    )
-    rev = r.stdout.strip()
-
-    if rev:
+    if rev := r.stdout.strip():
         # Check if repo is dirty
         if run_wrapper(
             ["git", "-C", nixpkgs_path, "diff", "--quiet"],

pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_main.py

@@ -74,8 +74,7 @@ def test_parse_args() -> None:
 
 @patch.dict(nr.process.os.environ, {}, clear=True)
 @patch(get_qualified_name(nr.process.subprocess.run), autospec=True)
-@patch(get_qualified_name(nr.nix.shutil.which), autospec=True, return_value="/bin/git")
-def test_execute_nix_boot(mock_which: Any, mock_run: Any, tmp_path: Path) -> None:
+def test_execute_nix_boot(mock_run: Any, tmp_path: Path) -> None:
     nixpkgs_path = tmp_path / "nixpkgs"
     nixpkgs_path.mkdir()
     config_path = tmp_path / "test"

pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_nix.py

@@ -57,8 +57,7 @@ def test_edit(mock_run: Any, monkeypatch: Any, tmpdir: Any) -> None:
         mock_run.assert_called_with(["editor", default_nix], check=False)
 
 
-@patch(get_qualified_name(n.shutil.which), autospec=True, return_value="/bin/git")
-def test_get_nixpkgs_rev(mock_which: Any) -> None:
+def test_get_nixpkgs_rev() -> None:
     assert n.get_nixpkgs_rev(None) is None
 
     path = Path("/path/to/nix")