It would be great if yasnippet will provide continuous creating and appending new fields to a snippet.
For example, snippet for a tuple of strings in python. Snippet with name strtuple firstly replaced to:
('**cursor is here**')
when i press <tab> yasnippet authomatically creates new field:
('first string', '**now cursor is here**')
and so on:
('first string', 'second string', '**cursor is here**')
For finishing snippet just move cursor or press C-g.
Merging with #295.