Comment 1 for bug 510232

After discussing the issue with Manuel de la Peña, I think the best solution would be to allow regular list values in desktopcouch records, and treat any list value in json as a regular list by default, then providing API to explicitly assign a mergeable list type value to a key in desktopcouch.

For this to work, we should put an "_is_mergeable_list": true property on each mergeable list json representation, rather than relying on the form of the keys to resemble uuids. (we should keep the checks in place that they are though.)

This automatically lifts the restrictions that you can't have empty mergeable list values as well, since the presence of the key would tell you that it is of this type.

The key is ugly, but unlikely to clash in practice, and what we have in place isn't any better.