Re: [PATCH v2 2/4] Add find_insert_index, insert_at_index and clear_func functions to string_list

> string_list_find_insert_index() and string_list_insert_at_index() enables you to see if an item is in the string_list, and to insert at the appropriate index in the list, if not there.
> This is usefull if you need to manipulate an existing item, if present, and insert a new item if not.
>
> Future mailmap code will use this construct to enable complex (old_name, old_email) -> (new_name, new_email) lookups.
>
> The string_list_clear_func() allows to call a custom cleanup function on each item in a string_list, which is useful is the util member points to a complex structure.