rails/rails — pull request #8445 by claudiob (2012-12-07 09:33:17+00:00)
Title: Update #where rdoc to match 6ba0f97

This commit updates the rdoc of AR#where to match the changes applied
in https://github.com/rails/rails/commit/6ba0f97 that is:

* `where(nil)` has the same effect of `where('')`: a no op
* `where` (no args) has the same effect of `where(:chain)`: to create a WhereChain