### Please describe the problem.
Two direct mode repos both on crippled filesystem (NTFS), although no file is modified, each "git annex sync" command will generate a new commit on master branch, which makes "git log" grow fast.

### What steps will reproduce the problem?
Run the script below on NTFS filesystem

### What version of git-annex are you using? On what operating system?
I tried multiple combination:
git version from 2.7.4 to 2.11.0;
git-annex version from 5.20150812 to 6.20161211;
OS includes ubuntu xenial&yakkety and Windows 10;
As long as the script is run on NTFS filesystem it reproudces the problem.
However, on non crippled file system the script works without problem.

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log
mkdir a
cd a
git init
git annex init first
git annex direct
echo foo > 1.txt
git annex add .
git annex sync
cd ..
git clone a b
cd b
git annex init second
git annex direct
git annex sync
cd ../a
git remote add second ../b
git annex sync
echo bar > 2.txt
git annex add 2.txt
git annex sync
cd ../b
git annex sync
cd ../a
git annex sync
cd ../b
git annex sync
cd ../a
git annex sync
cd ../b
git annex sync
cd ../a
git annex sync
cd ../b
git annex sync
cd ../a
git annex sync
cd ../b
git annex sync
cd ../a
git annex sync
cd ../b
git annex sync
cd ../a
git annex sync
cd ../b
git annex sync
git log | grep refs/heads/synced/master | wc


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

I'm new to git-annex and immediately astonished by its unique strength. I fit the Archivist use case, and this could be the solution I wanted for so long. I'm planning to deploy it on 2 Windows boxes and several USB disks, all of them on NTFS. I learnt the idea that v6 repo is not yet good for Win/NTFS (double disk space), so I guess direct mode is the way to go? I have already got some test repos running and practicing, indeed this sync loop problem is the only remaining case I'm not confident with. Is it a bug or some safety measure feature? Am I good to go? Thanks and oh, Merry X'mas!