Nested projects cause confusing "no package found in source" message

[seth]

A project containing a subdirectory containing a copy of the top-level project fails to build. The message given to the user (with --verbose) is: "no package found in source".

Here's a sample project repo that reproduces the issue:
https://github.com/seth/nested-rust-ex1

I encountered this issue "in the wild" while working on delivery-cli:
https://github.com/chef/delivery-cli
While this may seem super obscure, it is something I hit and I wasn't intentionally trying to created a bogus project structure. What happens is that a build tool (omnibus) creates the nested copy while producing OS packages and leaves it behind.

I think the behavior is somewhat new and that such directories were ignored in previous versions of cargo.

[carols10cents]

This looks like it was fixed by #1780 but just not closed automatically. I tried reproducing and could not! Closing!