Re: false positives from git diff-index when used with --git-dir

[Jeff King <peff@peff.net>]

On Thu, Oct 14, 2010 at 06:40:51PM +0400, Alexander Gladysh wrote:

> I'm *sometimes* (once in about ten times I use it -- repository
> changes between invocations of course) getting false positives from
> git diff-index when I invoke git from another directory:
> 
> git --git-dir=path/to/.git --work-tree=path/to update-index -q --refresh
> git --git-dir=path/to/.git --work-tree=path/to diff-index --exit-code
> --quiet HEAD
> 
> This is *really* annoying and really kills the benifits from my
> workflow automation scripts.
> 
> Unfortunately I can't find a reproducible use case for this bug.
> 
> Is there anything I can do to help catch it?

Can it reproduce over a large number of trials? I.e., something like:

  while true; do
    git ... update-index ...
    git ... diff-index ... || echo failed
  done

If so, try adding a "sleep 1" between the two commands. If that fixes
it, it implies a race condition in git.

You could also try running under valgrind to see if there are any bad
memory accesses, which could also produce intermittent buggy behavior.

-Peff