"git diff --no-pager --exit-code" errors out but returns zero exit code

[Romain Chossart <romainchossart@xxxxxxxxx>]

I recently found out (the hard way :-) ) that running the following
command prints an appropriate error on stderr but returns a zero exit
code:

> $ git diff --no-pager --exit-code
> error: invalid option: --no-pager
> $ echo $?
> 0

I would expect a non-zero exit code to be returned.

Interestingly, running `git diff --no-pager --exit-code HEAD` shows a
usage instead and does return a non-zero exit code as expected.

Thanks,
-- 
Romain Chossart