Auto merge of #5152 - matklad:clap, r=alexcrichton

Clap

Reopening of #5129

So, looks like all tests are :green_apple: on my machine!

I definitely want to refactor it some more, and also manually checked that we haven't regressed any help messages, but all the major parts are in place already.

diff --cc Cargo.toml
Simple merge

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

diff --cc src/cargo/ops/cargo_doc.rs
Simple merge

diff --cc src/cargo/ops/cargo_generate_lockfile.rs
Simple merge

diff --cc src/cargo/ops/cargo_install.rs
Simple merge

diff --cc src/cargo/ops/cargo_run.rs
index f4c6c71ad3e4a703698a46cd0e99812e2aea0345,cfd26e7524ba3610ce21b4e64ae6f9f55c87eda5..1858dab7801fb76f13b25140854479ec762d3dc4
--- 1/src/cargo/ops/cargo_run.rs
--- 2/src/cargo/ops/cargo_run.rs
+++ b/src/cargo/ops/cargo_run.rs
@@@ -13,10 -13,10 +13,10 @@@ pub fn run(ws: &Workspace
          Packages::All |
          Packages::Default |
          Packages::OptOut(_) => unreachable!("cargo run supports single package only"),
-         Packages::Packages(xs) => match xs.len() {
+         Packages::Packages(ref xs) => match xs.len() {
              0 => ws.current()?,
              1 => ws.members()
 -                .find(|pkg| pkg.name() == xs[0])
 +                .find(|pkg| &*pkg.name() == xs[0])
                  .ok_or_else(||
                      format_err!("package `{}` is not a member of the workspace", xs[0])
                  )?,

diff --cc tests/testsuite/build.rs
Simple merge