diff -r 9b3f95d9783d -r beede158ea8a mercurial/windows.py
--- a/mercurial/windows.py	Fri Dec 22 23:17:04 2017 +0800
+++ b/mercurial/windows.py	Sat Dec 30 21:07:03 2017 -0500
@@ -226,6 +226,13 @@
 def checklink(path):
     return False
 
+def getfstype(dirpath):
+    '''Get the filesystem type name from a directory (best-effort)
+
+    Returns None if we are unsure. Raises OSError on ENOENT, EPERM, etc.
+    '''
+    return None
+
 def setbinary(fd):
     # When run without console, pipes may expose invalid
     # fileno(), usually set to -1.