Auto merge of #4957 - sfackler:registry-elaboration, r=alexcrichton
authorbors <bors@rust-lang.org>
Thu, 25 Jan 2018 00:37:01 +0000 (00:37 +0000)
committerbors <bors@rust-lang.org>
Thu, 25 Jan 2018 00:37:01 +0000 (00:37 +0000)
Elaborate registry names to index URLs when publishing

This avoids introducing a dependency on the publisher's name for the
registry.

Closes #4880


Trivial merge