[BUG] "git apply --index" with missing --directory option silently does nothing

When applying a patch file for a subtree of a git repo, where was
required is "git apply --index --directory=...", if the user forgets
to add the --directory flag, then git should bomb out saying it cannot
apply the patch.

But what happens is that nothing happens, and git stays silent about
having done nothing:

~/softs/tmp/linux-2.6.32$ git rev-parse --git-dir
/home/localadm/softs/tmp/.git
~/softs/tmp/linux-2.6.32$ bzcat /home/localadm/Downloads/patch-2.6.32.28.bz2 | git apply --index --whitespace=nowarn
~/softs/tmp/linux-2.6.32$ echo $?
0
~/softs/tmp/linux-2.6.32$ git status
# On branch master
nothing to commit (working directory clean)

-- 
Yann Dirson - Bertin Technologies