Merge branch 'rs/parse-options-help-text-is-optional'

It may be tempting to leave the help text NULL for a command line
option that is either hidden or too obvious, but "git subcmd -h"
and "git subcmd --help-all" would have segfaulted if done so.  Now
the help text is optional.

* rs/parse-options-help-text-is-optional:
  parse-options: allow omitting option help text

parse-options.c

@@ -1186,14 +1186,15 @@ static enum parse_opt_result usage_with_options_internal(struct parse_opt_ctx_t
 			continue;
 		}
 
-		for (cp = _(opts->help); *cp; cp = np) {
+		for (cp = opts->help ? _(opts->help) : ""; *cp; cp = np) {
 			np = strchrnul(cp, '\n');
-			usage_padding(outfile, pos);
-			fprintf(outfile, "%.*s\n", (int)(np - cp), cp);
 			if (*np)
 				np++;
+			usage_padding(outfile, pos);
+			fwrite(cp, 1, np - cp, outfile);
 			pos = 0;
 		}
+		fputc('\n', outfile);
 
 		if (positive_name) {
 			if (find_option_by_long_name(all_opts, positive_name))