[hooks/symlinks] use git-ls to walk to-be-checked files

fixes #2

hooks/pre-commit.d/02-detect-broken-symlinks.py

@@ -7,6 +7,8 @@ with status 1. If none are found exit with status 0.
 import sys
 import os
 from pathlib import Path
+import subprocess
+
 
 def _resolve(path):
     try:
@@ -18,21 +20,21 @@ def _resolve(path):
         except FileNotFoundError:
             return Path(os.readlink(str(path)))
 
+
 broken = []
-for root, dirs, files in os.walk('.'):
-    if root.startswith('./.git'):
-        # Ignore the .git directory.
+files = subprocess.check_output(['git', 'ls-files'],
+                                   universal_newlines=True)
+root = os.getcwd()
+for filename in files.splitlines():
+    path = Path(os.path.join(root,filename))
+    if path.is_symlink():
+        target = _resolve(path)
+        # exists already checks if the pointed to file is there
+        if not path.exists():
+            broken.append('{} --> {}'.format(path, target))
+    else:
+        # If it's not a symlink we're not interested.
         continue
-    for filename in files:
-        path = Path(os.path.join(root,filename))
-        if path.is_symlink():
-            target = _resolve(path)
-            # exists already checks if the pointed to file is there
-            if not path.exists():
-                broken.append('{} --> {}'.format(path, target))
-        else:
-            # If it's not a symlink we're not interested.
-            continue
 
 if len(broken) == 0:
     sys.exit(0)