parse-options: only insert newline in help text if needed

Currently, when parse_options() produces a help message it always emits
a blank line after the usage text to separate it from the options text.
If the option spec does not define any switches, or only defines hidden
switches that will not be displayed, then the help text will end up with
two trailing blank lines instead of one.  Let's defer emitting the blank
line between the usage text and the options text until it is clear that
the options section will not be empty.

Fixes t1502.5, t1502.6.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

parse-options.c

@@ -581,6 +581,7 @@ static int usage_with_options_internal(struct parse_opt_ctx_t *ctx,
 				       const struct option *opts, int full, int err)
 {
 	FILE *outfile = err ? stderr : stdout;
+	int need_newline;
 
 	if (!usagestr)
 		return PARSE_OPT_HELP;
@@ -603,8 +604,7 @@ static int usage_with_options_internal(struct parse_opt_ctx_t *ctx,
 		usagestr++;
 	}
 
-	if (opts->type != OPTION_GROUP)
-		fputc('\n', outfile);
+	need_newline = 1;
 
 	for (; opts->type != OPTION_END; opts++) {
 		size_t pos;
@@ -612,6 +612,7 @@ static int usage_with_options_internal(struct parse_opt_ctx_t *ctx,
 
 		if (opts->type == OPTION_GROUP) {
 			fputc('\n', outfile);
+			need_newline = 0;
 			if (*opts->help)
 				fprintf(outfile, "%s\n", _(opts->help));
 			continue;
@@ -619,6 +620,11 @@ static int usage_with_options_internal(struct parse_opt_ctx_t *ctx,
 		if (!full && (opts->flags & PARSE_OPT_HIDDEN))
 			continue;
 
+		if (need_newline) {
+			fputc('\n', outfile);
+			need_newline = 0;
+		}
+
 		pos = fprintf(outfile, "    ");
 		if (opts->short_name) {
 			if (opts->flags & PARSE_OPT_NODASH)

t/t1502-rev-parse-parseopt.sh

@@ -98,7 +98,7 @@ END_EXPECT
 	test_i18ncmp expect output
 '
 
-test_expect_failure 'test --parseopt help output no switches' '
+test_expect_success 'test --parseopt help output no switches' '
 	sed -e "s/^|//" >expect <<\END_EXPECT &&
 |cat <<\EOF
 |usage: some-command [options] <args>...
@@ -111,7 +111,7 @@ END_EXPECT
 	test_i18ncmp expect output
 '
 
-test_expect_failure 'test --parseopt help output hidden switches' '
+test_expect_success 'test --parseopt help output hidden switches' '
 	sed -e "s/^|//" >expect <<\END_EXPECT &&
 |cat <<\EOF
 |usage: some-command [options] <args>...