git apply fails silently when on the wrong directory

I recently ran into a similar issue as described here:

https://stackoverflow.com/questions/24821431/git-apply-patch-fails-silently-no-errors-but-nothing-happens

I was using the alias:

alias ganw='git diff -U0 -w --no-color "$@" | git apply --cached --ignore-whitespace --unidiff-zero -'

to stage non-whitespace changes, but I was not in the root directory and
the changes were not being applied. I broke down the command to discover
the 'git apply' part of the pipe was silently failing to apply anything,
exiting 0 without even a warning.

The exit status and lack of warning is terribly misleading, I imagine
this would be the cause of subtle bugs in automated scripts. 

Is this expected behaviour?

Thanks,

Ernesto