RFC patch, 4 partsRe-implement 'git remote update' using 'git fetch'

diff --git a/builtin-remote.c b/builtin-remote.c
index 0777dd7..fd7e0b2 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -1189,88 +1189,54 @@ static int prune_remote(const char *remote, int dry_run)
 	return result;
 }
 
-static int get_one_remote_for_update(struct remote *remote, void *priv)
+static int get_remote_default(const char *key, const char *value, void *priv)
 {
-	struct string_list *list = priv;
-	if (!remote->skip_default_update)
-		string_list_append(remote->name, list);
-	return 0;
-}
-
-static struct remote_group {
-	const char *name;
-	struct string_list *list;
-} remote_group;
-
-static int get_remote_group(const char *key, const char *value, void *num_hits)
-{
-	if (!prefixcmp(key, "remotes.") &&
-			!strcmp(key + 8, remote_group.name)) {
-		/* split list by white space */
-		int space = strcspn(value, " \t\n");
-		while (*value) {
-			if (space > 1) {
-				string_list_append(xstrndup(value, space),
-						remote_group.list);
-				++*((int *)num_hits);
-			}
-			value += space + (value[space] != '\0');
-			space = strcspn(value, " \t\n");
-		}
+	if (strcmp(key, "remotes.default") == 0) {
+		int *found = priv;
+		*found = 1;
 	}
-
 	return 0;
 }
 
 static int update(int argc, const char **argv)
 {
-	int i, result = 0, prune = 0;
-	struct string_list list = { NULL, 0, 0, 0 };
-	static const char *default_argv[] = { NULL, "default", NULL };
+	int i, prune = 0;
 	struct option options[] = {
 		OPT_GROUP("update specific options"),
 		OPT_BOOLEAN('p', "prune", &prune,
 			    "prune remotes after fetching"),
 		OPT_END()
 	};
+	const char **fetch_argv;
+	int fetch_argc = 0;
+	int default_defined = 0;
+
+	fetch_argv = xmalloc(sizeof(char *) * (argc+4));
 
 	argc = parse_options(argc, argv, NULL, options, builtin_remote_usage,
 			     PARSE_OPT_KEEP_ARGV0);
-	if (argc < 2) {
-		argc = 2;
-		argv = default_argv;
-	}
 
-	remote_group.list = &list;
-	for (i = 1; i < argc; i++) {
-		int groups_found = 0;
-		remote_group.name = argv[i];
-		result = git_config(get_remote_group, &groups_found);
-		if (!groups_found && (i != 1 || strcmp(argv[1], "default"))) {
-			struct remote *remote;
-			if (!remote_is_configured(argv[i]))
-				die("No such remote or remote group: %s",
-				    argv[i]);
-			remote = remote_get(argv[i]);
-			string_list_append(remote->name, remote_group.list);
-		}
-	}
+	fetch_argv[fetch_argc++] = "fetch";
 
-	if (!result && !list.nr  && argc == 2 && !strcmp(argv[1], "default"))
-		result = for_each_remote(get_one_remote_for_update, &list);
+	if (verbose)
+		fetch_argv[fetch_argc++] = "-v";
+	if (argc < 2) {
+		fetch_argv[fetch_argc++] = "default";
+	} else {
+		fetch_argv[fetch_argc++] = "--multiple";
+		for (i = 1; i < argc; i++)
+			fetch_argv[fetch_argc++] = argv[i];
+	}
 
-	for (i = 0; i < list.nr; i++) {
-		int err = fetch_remote(list.items[i].string);
-		result |= err;
-		if (!err && prune)
-			result |= prune_remote(list.items[i].string, 0);
+	if (strcmp(fetch_argv[fetch_argc-1], "default") == 0) {
+		git_config(get_remote_default, &default_defined);
+		if (!default_defined)
+			fetch_argv[fetch_argc-1] = "--all";
 	}
 
-	/* all names were strdup()ed or strndup()ed */
-	list.strdup_strings = 1;
-	string_list_clear(&list, 0);
+	fetch_argv[fetch_argc] = NULL;
 
-	return result;
+	return run_command_v_opt(fetch_argv, RUN_GIT_CMD);
 }
 
 static int get_one_entry(struct remote *remote, void *priv)