diff -r e7a02e9ad162 -r 6262e30b0c09 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Sun Mar 12 01:03:23 2017 -0800
+++ b/mercurial/debugcommands.py	Sun Mar 12 01:34:17 2017 -0800
@@ -790,6 +790,10 @@
     """show information detected about current filesystem"""
     util.writefile('.debugfsinfo', '')
     ui.write(('exec: %s\n') % (util.checkexec(path) and 'yes' or 'no'))
+    from . import osutil
+    if util.safehasattr(osutil, 'getfstype'):
+        fstype = osutil.getfstype('.')
+        ui.write(('fstype: %s\n') % (fstype or '(unknown)'))
     ui.write(('symlink: %s\n') % (util.checklink(path) and 'yes' or 'no'))
     ui.write(('hardlink: %s\n') % (util.checknlink(path) and 'yes' or 'no'))
     ui.write(('case-sensitive: %s\n') % (util.fscasesensitive('.debugfsinfo')