Possible timestamp problems with diff-files?

For our Git client, we are invoking

git diff-files--quiet --ignore-submodules

immediately after a commit of *all* changes. Hence, the expected exit
code would be 0 (because there are no changes). A user has now reported
that for commits with many changes, exit code is sometimes 1. For the
last incident, the commit was started at 15:24:11,820 and finished at
15:24:12,329, diff-files was invoked at 15:24:12,455 and failed with
exit code 1 at 15:24:21,394. A subsequent diff-files succeeded, so I'm
wondering now, if that could be a timestamp problem (maybe related to
the Index)?

Note that there are a couple of threads running in the client itself, so
I guess actual running time of diff-files was much shorter than 9
seconds and chances are that some parts of diff-files were run in the
same second 15:24:12.

System configuration is:
Linux splitter 2.6.38-11-server #48-Ubuntu SMP Fri Jul 29 19:20:32 UTC
2011 x86_64 x86_64 x86_64 GNU/Linux

git version 1.7.4.1

--
Best regards,
Marc Strapetz
=============
syntevo GmbH
http://www.syntevo.com
http://blog.syntevo.com