[GSoC] parse: not show usage help when invalid id

> patch for too chatty command when <id> is invalid
> ex. git tag --contains <id>
>
> It is possible to skip 'goto show_usage_error' when
> parse_long_opt fails? and return directly from there.

>
> Signed-off-by: Roger Solano <sc_rogeralberto@hotmail.com>
> ---
>  parse-options.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/parse-options.c b/parse-options.c
> index 125e84f98..074915eb3 100644
> --- a/parse-options.c
> +++ b/parse-options.c
> @@ -550,7 +550,7 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
>  			goto show_usage;
>  		switch (parse_long_opt(ctx, arg + 2, options)) {
>  		case -1:
> -			goto show_usage_error;
> +			return -1; 
>  		case -2:
>  			goto unknown;
>  		}