git-diff not showing changes (corrupt repo?)

Hi, A small personal git repository has started lying to me about changed files. git-diff sometimes tells me that the index has no changes from HEAD, while other commands (git-status, at least) seem to tell the truth. It is the same after I commit the new changes--at that point, "git-diff-tree HEAD^ HEAD -p" spits out a nice patch, but "git-diff HEAD^ HEAD" gives nothing.

I have tried git versions 1.5.1.6-1.5.3.3, and they all act the same, so I think the repository is corrupt. Does sound familiar to anybody? If this is user error (for example, "git-reset --hard HEAD^" on a branch that had already been pulled into another branch), I can restore from a recent backup and redo some changes, but I would like to help troubleshoot this behavior if it is a git bug. Is this a known behavior? git-fsck doesn't reveal anything amiss, besides dangling objects. Does anybody know anything about this situation or what can cause it?

Example of behavior:

$ git status # On branch bak_linear-checks3 nothing to commit (working directory clean) $ echo "test" >> Makefile $ git status # On branch bak_linear-checks3 # Changed but not updated: # (use "git add <file>..." to update what will be committed) # # modified: Makefile # no changes added to commit (use "git add" and/or "git commit -a") $ git diff $

Thanks, Dan