Auto merge of #10000 - alexcrichton:upgrade-edition, r=Eh2406

Upgrade Cargo to the 2021 edition

While I was poking around in the manifests I also went ahead and removed the `authors` entries since at least the one for Cargo itself is quite outdated and Cargo otherwise doesn't use these any more.

Author: bors

.github/workflows/main.yml

@@ -68,7 +68,9 @@ jobs:
 
     # Deny warnings on CI to avoid warnings getting into the codebase.
     - run: cargo test --features 'deny-warnings'
-    - run: cargo test --features 'deny-warnings' -p cargo-test-support
+    - run: cargo test --features 'deny-warnings' --manifest-path crates/cargo-test-support/Cargo.toml
+      env:
+        CARGO_TARGET_DIR: target
     - run: cargo test -p cargo-platform
     - run: cargo test -p cargo-util
     - run: cargo test --manifest-path crates/mdman/Cargo.toml
@@ -113,6 +115,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - run: rustup update nightly && rustup default nightly
+    - run: rustup update stable
     - run: rustup component add rust-docs
     - run: ci/validate-man.sh
     # This requires rustfmt, use stable.

Cargo.toml

@@ -1,10 +1,7 @@
 [package]
 name = "cargo"
 version = "0.59.0"
-edition = "2018"
-authors = ["Yehuda Katz <wycats@gmail.com>",
-           "Carl Lerche <me@carllerche.com>",
-           "Alex Crichton <alex@alexcrichton.com>"]
+edition = "2021"
 license = "MIT OR Apache-2.0"
 homepage = "https://crates.io"
 repository = "https://github.com/rust-lang/cargo"

benches/benchsuite/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "benchsuite"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/rust-lang/cargo"
 repository = "https://github.com/rust-lang/cargo"

benches/capture/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "capture"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "Tool for capturing a real-world workspace for benchmarking."
 

crates/cargo-platform/Cargo.toml

@@ -1,8 +1,7 @@
 [package]
 name = "cargo-platform"
 version = "0.1.2"
-authors = ["The Cargo Project Developers"]
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/rust-lang/cargo"
 repository = "https://github.com/rust-lang/cargo"

crates/cargo-test-macro/Cargo.toml

@@ -1,8 +1,7 @@
 [package]
 name = "cargo-test-macro"
 version = "0.1.0"
-authors = ["Jethro Beekman <jethro@fortanix.com>"]
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/rust-lang/cargo"
 repository = "https://github.com/rust-lang/cargo"

crates/cargo-test-support/Cargo.toml

@@ -1,9 +1,8 @@
 [package]
 name = "cargo-test-support"
 version = "0.1.0"
-authors = ["Alex Crichton <alex@alexcrichton.com>"]
 license = "MIT OR Apache-2.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
@@ -24,3 +23,6 @@ tar = { version = "0.4.18", default-features = false }
 termcolor = "1.1.2"
 toml = "0.5.7"
 url = "2.2.2"
+
+[features]
+deny-warnings = []

crates/cargo-test-support/src/lib.rs

@@ -5,6 +5,7 @@
 #![allow(clippy::all)]
 #![warn(clippy::needless_borrow)]
 #![warn(clippy::redundant_clone)]
+#![cfg_attr(feature = "deny-warnings", deny(warnings))]
 
 use std::env;
 use std::ffi::OsStr;

crates/cargo-util/Cargo.toml

@@ -1,8 +1,7 @@
 [package]
 name = "cargo-util"
 version = "0.1.1"
-authors = ["The Cargo Project Developers"]
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/rust-lang/cargo"
 repository = "https://github.com/rust-lang/cargo"

crates/crates-io/Cargo.toml

@@ -1,8 +1,7 @@
 [package]
 name = "crates-io"
 version = "0.33.0"
-edition = "2018"
-authors = ["Alex Crichton <alex@alexcrichton.com>"]
+edition = "2021"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/cargo"
 description = """