t1450-fsck (sometimes/often) failes on Mac OS X

From: Torsten Bögershausen <tboegi@web.de>
Date: Jul 14, 2012, 12:21 UTC
Message-ID: <5001644F.10901@web.de>

I saw the problem first on pu, some time ago, but it dissappeared after cloning git.git into another directory.

Now it appeared on next as well, so it's time to look a little bit deeper.

This test case of t1450 fails: test_expect_success 'tag pointing to something else than its type' '

To debug more, I added an exit 0 here to inspect the file named out:

diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 5b79c51..f1f45c9 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -179,6 +179,7 @@ test_expect_success 'tag pointing to something else than its type' '
        test_when_finished "git update-ref -d refs/tags/wrong" &&
        test_must_fail git fsck --tags 2>out &&
        cat out &&
+       exit 0
        grep "error in tag.*broken links" out
 '

Linux:
error: Object 63499e4ea8e096b831515ceb1d5a7593e4d87ae5 is a blob, not a commit
error in tag 66f6581d549f70e05ca586bc2df5c15a95662c36: broken links
error in tag 66f6581d549f70e05ca586bc2df5c15a95662c36: could not load tagged object

Mac OS X:
error: Object 63499e4ea8e096b831515ceb1d5a7593e4d87ae5 is a commit, not a blob
error: 63499e4ea8e096b831515ceb1d5a7593e4d87ae5: object corrupt or missing

I reverted the last change in fsck.c (Use the streaming interface), but that doesn't help

Looking into the trash directory and looking at the files, we can see that the .git/index is different
between Linux and Mac OS X.

Is there a good way to debug the index file?

BTW:  git bisect pointed out: 
 [76759c7dff53e8c84e975b88cb8245587c14c7ba] git on Mac OS and precomposed unicode
But re-running t1450 makes it pass, so that bisect went into the wrong direction
somewhere.

It seems that t1450 is timing depending, sometimes it passes, sometimes not.
And once it went into the state "non passed", it stays there.

It feels that I got stuck, any hints how to debug this further, please ?

/Torsten