Auto merge of #5070 - Eh2406:clippy, r=alexcrichton

Some Clippy suggestions

This is just some suggestions from Clippy and intellij rust.

Clippy still has a lot to say, but this is some of the simple things.

diff --cc src/bin/doc.rs
Simple merge

diff --cc src/cargo/lib.rs
Simple merge

diff --cc src/cargo/sources/git/utils.rs
Simple merge

diff --cc src/cargo/sources/registry/remote.rs
Simple merge