There are two proposals.

You seem to refer to the Google doc proposal that was linked to in the first message of the mailing list thread several months ago.

The link on hackernews points to an answer by Google that was written just a few hours ago that instead "propose" the following:

> If there is a source directory d/vendor, then, when compiling a source file within the subtree rooted at d, import "p" is interpreted as import "d/vendor/p" if that exists.