Not working when a repo has been partially restored with yarn

[michaeldisaro]

Consider the following repo structure:

Project1
-- node_modules
---- Project2
------ node_modules
-------- Project3
Project2
-- node_modules
Project3
-- node_modules

When working on Project2 we clean a previously linked node_modules and lose link to Project3 by re-downloading it from package manager.

If we call link/unlink on Project1 the command will throw.

TODO: Consider to pass an option to restore node_modules from package manager before linking, or to partially restore packages if no link is found when unlinking.