git-clean: add select by numbers interactive action

Draw a multiple choice menu using `list_and_choose` to select items
to be deleted by numbers.

User can input:

 *  1,5-7 : select 1,5,6,7 items to be deleted
 *  *     : select all items to be deleted
 *  -*    : unselect all, nothing will be deleted
 *        : (empty) finish selecting, and return back to main menu

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clean.c

@@ -680,6 +680,43 @@ static int filter_by_patterns_cmd(void)
 	return 0;
 }
 
+static int select_by_numbers_cmd(void)
+{
+	struct menu_opts menu_opts;
+	struct menu_stuff menu_stuff;
+	struct string_list_item *items;
+	int *chosen;
+	int i, j;
+
+	menu_opts.header = NULL;
+	menu_opts.prompt = N_("Select items to delete");
+	menu_opts.flags = 0;
+
+	menu_stuff.type = MENU_STUFF_TYPE_STRING_LIST;
+	menu_stuff.stuff = &del_list;
+	menu_stuff.nr = del_list.nr;
+
+	chosen = list_and_choose(&menu_opts, &menu_stuff);
+	items = del_list.items;
+	for (i = 0, j = 0; i < del_list.nr; i++) {
+		if (i < chosen[j]) {
+			*(items[i].string) = '\0';
+		} else if (i == chosen[j]) {
+			/* delete selected item */
+			j++;
+			continue;
+		} else {
+			/* end of chosen (chosen[j] == EOF), won't delete */
+			*(items[i].string) = '\0';
+		}
+	}
+
+	string_list_remove_empty_items(&del_list, 0);
+
+	free(chosen);
+	return 0;
+}
+
 static int quit_cmd(void)
 {
 	string_list_clear(&del_list, 0);
@@ -693,6 +730,7 @@ static int help_cmd(void)
 	printf_ln(_(
 		    "clean               - start cleaning\n"
 		    "filter by pattern   - exclude items from deletion\n"
+		    "select by numbers   - select items to be deleted by numbers\n"
 		    "quit                - stop cleaning\n"
 		    "help                - this screen\n"
 		    "?                   - help for prompt selection"
@@ -709,6 +747,7 @@ static void interactive_main_loop(void)
 		struct menu_item menus[] = {
 			{'c', "clean",			0, clean_cmd},
 			{'f', "filter by pattern",	0, filter_by_patterns_cmd},
+			{'s', "select by numbers",	0, select_by_numbers_cmd},
 			{'q', "quit",			0, quit_cmd},
 			{'h', "help",			0, help_cmd},
 		};