Re: [PATCH v3 03/10] parse-options.[ch]: consistently use "enum parse_opt_result"

> Use the "enum parse_opt_result" instead of an "int flags" as the
> return value of the applicable functions in parse-options.c.
> 
> This will help catch future bugs, such as the missing "case" arms in
> the two existing users of the API in "blame.c" and "shortlog.c". A
> third caller in 309be813c9b (update-index: migrate to parse-options
> API, 2010-12-01) was already checking for these.
> 
> As can be seen when trying to sort through the deluge of warnings
> produced when compiling this with CC=g++ (mostly unrelated to this
> change) we're not consistently using "enum parse_opt_result" even now,
> i.e. we'll return error() and "return 0;". See f41179f16ba
> (parse-options: avoid magic return codes, 2019-01-27) for a commit
> which started changing some of that.
> 
> I'm not doing any more of that exhaustive migration here, and it's
> probably not worthwhile past the point of being able to check "enum
> parse_opt_result" in switch().
> 
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---

> diff --git a/parse-options.c b/parse-options.c
> index 9c8ba963400..f718242096c 100644
> --- a/parse-options.c
> +++ b/parse-options.c
> @@ -699,13 +699,14 @@ static void free_preprocessed_options(struct option *options)
>  	free(options);
>  }
>  
> -static int usage_with_options_internal(struct parse_opt_ctx_t *,
> -				       const char * const *,
> -				       const struct option *, int, int);
> -
> -int parse_options_step(struct parse_opt_ctx_t *ctx,
> -		       const struct option *options,
> -		       const char * const usagestr[])
> +static enum parse_opt_result usage_with_options_internal(struct parse_opt_ctx_t *,
> +							 const char * const *,
> +							 const struct option *,
> +							 int, int);
> +
> +enum parse_opt_result parse_options_step(struct parse_opt_ctx_t *ctx,
> +					 const struct option *options,
> +					 const char * const usagestr[])
>  {
>  	int internal_help = !(ctx->flags & PARSE_OPT_NO_INTERNAL_HELP);
>  
> @@ -839,10 +840,11 @@ int parse_options_end(struct parse_opt_ctx_t *ctx)
>  	return ctx->cpidx + ctx->argc;
>  }
>  
> -int parse_options(int argc, const char **argv, const char *prefix,
> -		  const struct option *options,
> -		  const char * const usagestr[],
> -		  enum parse_opt_flags flags)
> +enum parse_opt_result parse_options(int argc, const char **argv,