git --list-cmds: collect command list in a string_list

Instead of printing the command directly one by one, keep them in a
list and print at the end. This allows more modification before we
print out (e.g. sorting, removing duplicates or even excluding some
items).

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git.c

@@ -36,7 +36,7 @@ const char git_more_info_string[] =
 
 static int use_pager = -1;
 
-static void list_builtins(unsigned int exclude_option, char sep);
+static void list_builtins(struct string_list *list, unsigned int exclude_option);
 
 static int match_token(const char *spec, int len, const char *token)
 {
@@ -47,18 +47,24 @@ static int match_token(const char *spec, int len, const char *token)
 
 static int list_cmds(const char *spec)
 {
+	struct string_list list = STRING_LIST_INIT_DUP;
+	int i;
+
 	while (*spec) {
 		const char *sep = strchrnul(spec, ',');
 		int len = sep - spec;
 
 		if (match_token(spec, len, "builtins"))
-			list_builtins(0, '\n');
+			list_builtins(&list, 0);
 		else
 			die(_("unsupported command listing type '%s'"), spec);
 		spec += len;
 		if (*spec == ',')
 			spec++;
 	}
+	for (i = 0; i < list.nr; i++)
+		puts(list.items[i].string);
+	string_list_clear(&list, 0);
 	return 0;
 }
 
@@ -249,7 +255,13 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			(*argc)--;
 		} else if (skip_prefix(cmd, "--list-cmds=", &cmd)) {
 			if (!strcmp(cmd, "parseopt")) {
-				list_builtins(NO_PARSEOPT, ' ');
+				struct string_list list = STRING_LIST_INIT_DUP;
+				int i;
+
+				list_builtins(&list, NO_PARSEOPT);
+				for (i = 0; i < list.nr; i++)
+					printf("%s ", list.items[i].string);
+				string_list_clear(&list, 0);
 				exit(0);
 			} else {
 				exit(list_cmds(cmd));
@@ -533,14 +545,14 @@ int is_builtin(const char *s)
 	return !!get_builtin(s);
 }
 
-static void list_builtins(unsigned int exclude_option, char sep)
+static void list_builtins(struct string_list *out, unsigned int exclude_option)
 {
 	int i;
 	for (i = 0; i < ARRAY_SIZE(commands); i++) {
 		if (exclude_option &&
 		    (commands[i].option & exclude_option))
 			continue;
-		printf("%s%c", commands[i].cmd, sep);
+		string_list_append(out, commands[i].cmd);
 	}
 }