Unify cargo and rustc's error reporting

[jyn514]

Fixes rust-lang/rust#86854.

Don't print "run the command again with --verbose"

Here is a typical error seen by users of Cargo:

error[E0601]: `main` function not found in crate `wrong`
  |
  = note: consider adding a `main` function to `src/main.rs`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0601`.
error: could not compile `wrong`

To learn more, run the command again with --verbose.

The --verbose output is not particularly helpful in this case. The
error is unrelated to what cargo is doing, and passing --verbose will
not give useful information about how to proceed. Additionally, it's
unclear that --verbose is referring to the cargo command and not
rustc; this is especially true when cargo is wrapped by another build
system (such as Meson, x.py, or Make).

This omits the "run the command again with --verbose" output. --verbose
is still shown in cargo build --help, but it's not singled out above
all the other options.

Combine rustc and cargo's diagnostic summaries

This works by introspecting rustc's error output, using the JSON format
to determine whether it's a warning or error, then skipping it
altogether if it's a summary of the diagnostics printed.

Before:

$ cargo check --message-format short
src/main.rs:1:10: warning: trait objects without an explicit `dyn` are deprecated
src/main.rs:1:1: error[E0601]: `main` function not found in crate `wrong`
src/main.rs:1:9: error[E0038]: the trait `Clone` cannot be made into an object
error: aborting due to 2 previous errors; 1 warning emitted
error: could not compile `wrong`

After:

$ cargo check --message-format short
src/main.rs:1:10: warning: trait objects without an explicit `dyn` are deprecated
src/main.rs:1:1: error[E0601]: `main` function not found in crate `wrong`
src/main.rs:1:9: error[E0038]: the trait `Clone` cannot be made into an object
error: could not compile `wrong` due to 2 previous errors; 1 warning emitted

[rust-highfive]

r? @alexcrichton

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[jyn514]

The original example from rust-lang/rust#86854 now looks like this:

error[E0308]: mismatched types
 --> src/lib.rs:1:11
  |
1 | fn f() -> usize {}
  |    -      ^^^^^ expected `usize`, found `()`
  |    |
  |    implicitly returns `()` as its body has no tail or `return` expression

For more information about this error, try `rustc --explain E0308`.
error: could not compile `playground` due to previous error

[ehuss]

Looks good, I think this is a great improvement.

[ehuss]

Thanks!

@bors r+

[bors]

📌 Commit 9c7cc54 has been approved by ehuss

[bors]

⌛ Testing commit 9c7cc54 with merge cc80b40...

[bors]

☀️ Test successful - checks-actions
Approved by: ehuss
Pushing cc80b40 to master...