Auto merge of #5111 - ehuss:bashc-toolchains, r=alexcrichton
authorbors <bors@rust-lang.org>
Fri, 2 Mar 2018 20:42:25 +0000 (20:42 +0000)
committerbors <bors@rust-lang.org>
Fri, 2 Mar 2018 20:42:25 +0000 (20:42 +0000)
Support +toolchain rustup override in bash completions.

Fixes #5107


Trivial merge