Add more checks for mingw platform

When the mingw platform is detected, several different path routines will be applied.

pre_commit/resources/hook-tmpl

@@ -6,6 +6,7 @@ import distutils.spawn
 import os
 import subprocess
 import sys
+import sysconfig
 
 # work around https://github.com/Homebrew/homebrew-core/issues/30445
 os.environ.pop('__PYVENV_LAUNCHER__', None)
@@ -76,7 +77,10 @@ def _run_legacy():
 
 def _validate_config():
     cmd = ('git', 'rev-parse', '--show-toplevel')
-    top_level = subprocess.check_output(cmd).decode('UTF-8').strip()
+    top_level = fix_mingw_path(
+        subprocess.check_output(cmd).decode('UTF-8').
+        strip(),
+    )
     cfg = os.path.join(top_level, CONFIG)
     if os.path.isfile(cfg):
         pass
@@ -177,6 +181,21 @@ else:
     _subprocess_call = subprocess.call
 
 
+def is_mingw():
+    """Check whether platform is mingw or not."""
+    return sysconfig.get_platform() in 'mingw'
+
+
+def fix_mingw_path(path):
+    """Convert cygwin path to mingw-style path"""
+    if is_mingw():
+        path = subprocess.check_output([
+            'cygpath', '-m',
+            path,
+        ]).decode().strip()
+    return path
+
+
 def main():
     retv, stdin = _run_legacy()
     try: