Vim - how to fold indented lines into parent line, not underneath it

Question

With foldmethod=indent I can take this text:

1. Heading
2.    item one
3.    item two
4.    itme three

and fold lines 2, 3 and 4 to achieve this:

1. Heading
2. ------------------------------------------

where the dotted line is the collapsed lines.

How can I achieve this instead

1. Heading ----------------------------------

i.e. lines 2, 3 and 4 have collapsed into line 1.