Message about missing nightly components suggests using invalid command

[vi]

Problem
When rustup update nightly fails because of some components are unavailable, it now shows extended, more helpful message about choosing a other-dated nightly.

Hovewer, installation command mentioned at the end of that message is confusing:

info: syncing channel updates for 'nightly-x86_64-unknown-linux-gnu'
info: latest update on 2019-04-15, rust version 1.35.0-nightly (aa99abeb2 2019-04-14)
error: some components unavailable for download: 'rls', 'clippy'
if you require these components, please install and use the latest successful build version, which you can find at https://rust-lang-nursery.github.io/rust-toolstate, for example.
rustup install nightly-2018-12-27 for channel 'nightly'

I though that it does #1628 and tried this:

$ rustup install nightly-2019-04-15 for channel nightly
info: syncing channel updates for 'nightly-2019-04-15-x86_64-unknown-linux-gnu'
info: latest update on 2019-04-15, rust version 1.35.0-nightly (aa99abeb2 2019-04-14)
info: downloading component 'rustc'
 81.9 MiB /  88.3 MiB ( 93 %)   0 B/s ETA: Unknown                ^C

, meaning "Download nightly versioned 2019-04-15 and use it for channel nightly". But it's probably not what actually happens.

Steps

1. Have Rust nightly installed by rustup with many components
2. Try to update nightly when not all those components are available
3. Observe the error message and try to follow the command in it verbatim

Possible Solution(s)

Change layout of the message, indent that rustup install nightly-2018-12-27 or surround it with some quotation marks.

Notes

Related: #1628.

rustup --version && rustup show

rustup 1.17.0 (069c88ed6 2019-03-05)
Default host: x86_64-unknown-linux-gnu

installed toolchains
--------------------

stable-x86_64-unknown-linux-gnu
beta-x86_64-unknown-linux-gnu
nightly-x86_64-unknown-linux-gnu (default)
1.23.0-x86_64-unknown-linux-gnu
1.28.0-x86_64-unknown-linux-gnu
1.30.1-x86_64-unknown-linux-gnu

installed targets for active toolchain
--------------------------------------

aarch64-unknown-linux-gnu
aarch64-unknown-linux-musl
arm-linux-androideabi
arm-unknown-linux-gnueabi
arm-unknown-linux-musleabi
armv7-linux-androideabi
i586-unknown-linux-musl
i686-linux-android
i686-pc-windows-gnu
i686-unknown-freebsd
i686-unknown-linux-musl
mips-unknown-linux-musl
mipsel-unknown-linux-gnu
mipsel-unknown-linux-musl
wasm32-unknown-unknown
x86_64-apple-darwin
x86_64-apple-ios
x86_64-linux-android
x86_64-pc-windows-gnu
x86_64-unknown-freebsd
x86_64-unknown-linux-gnu
x86_64-unknown-linux-musl

active toolchain
----------------

nightly-x86_64-unknown-linux-gnu (default)
^[[6~^[[6~^[[5~^C
rust@vi-notebook:~$ { rustup --version && rustup show  } | xclip -in
> ^C
rust@vi-notebook:~$ { rustup --version && rustup show;  } | xclip -in
Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0
rust@vi-notebook:~$ { rustup --version && rustup show;  } 
rustup 1.17.0 (069c88ed6 2019-03-05)
Default host: x86_64-unknown-linux-gnu

installed toolchains
--------------------

stable-x86_64-unknown-linux-gnu
beta-x86_64-unknown-linux-gnu
nightly-x86_64-unknown-linux-gnu (default)
1.23.0-x86_64-unknown-linux-gnu
1.28.0-x86_64-unknown-linux-gnu
1.30.1-x86_64-unknown-linux-gnu

installed targets for active toolchain
--------------------------------------

aarch64-unknown-linux-gnu
aarch64-unknown-linux-musl
arm-linux-androideabi
arm-unknown-linux-gnueabi
arm-unknown-linux-musleabi
armv7-linux-androideabi
i586-unknown-linux-musl
i686-linux-android
i686-pc-windows-gnu
i686-unknown-freebsd
i686-unknown-linux-musl
mips-unknown-linux-musl
mipsel-unknown-linux-gnu
mipsel-unknown-linux-musl
wasm32-unknown-unknown
x86_64-apple-darwin
x86_64-apple-ios
x86_64-linux-android
x86_64-pc-windows-gnu
x86_64-unknown-freebsd
x86_64-unknown-linux-gnu
x86_64-unknown-linux-musl

active toolchain
----------------

nightly-x86_64-unknown-linux-gnu (default)
rustc 1.35.0-nightly (7c19e1eed 2019-03-12)