Daniel Shahaf wrote on Wed, Mar 09, 2016 at 13:24:44 +0000:
> Jun T. wrote on Mon, Mar 07, 2016 at 12:16:54 +0900:
> > In the case of
> > 
> > % git reset commit <TAB>    # commit is not HEAD
> > 
> > I have no idea what to do, so I just added __git_ignore_line
> > to the original code. 
> 
> I think you're looking for «git diff-index --cached -z --name-only
> $treeish».

Turns out there was already a helper function that did almost exactly
that, so we can just reuse it.  Patch attached.

I took the liberty of changing the tag and description you used, since
"staged files" isn't exactly right for this syntax: files that are in
$treeish but not staged may also be completed.

WDYT?

Thanks,

Daniel