message: Update some fix comments.
diff: //! to print at the same time).
  //!
  //! Cargo begins a normal `cargo check` operation with itself set as a proxy
  -//! for rustc by setting `cargo_as_rustc_wrapper` in the build config. When
  +//! for rustc by setting `rustc_wrapper` in the build config. When
  //! cargo launches rustc to check a crate, it is actually launching itself.
  //! The `FIX_ENV` environment variable is set so that cargo knows it is in
  -//! fix-proxy-mode. It also sets the `RUSTC` environment variable to the
  -//! actual rustc so Cargo knows what to execute.
  +//! fix-proxy-mode.
  //!
  //! Each proxied cargo-as-rustc detects it is in fix-proxy-mode (via `FIX_ENV`
  //! environment variable in `main`) and does the following:
  @@ -198,9 +197,8 @@ pub fn fix_maybe_exec_rustc() -> CargoResult<bool> {
  // That's very likely to only mean the crates in the workspace the user is
  // working on, not random crates.io crates.
  //
  - // To that end we only actually try to fix things if it looks like we're
  - // compiling a Rust file and it *doesn't* have an absolute filename. That's
  - // not the best heuristic but matches what Cargo does today at least.
  + // The master cargo process tells us whether or not this is a "primary"
  + // crate via the CARGO_PRIMARY_PACKAGE environment variable.
  let mut fixes = FixedCrate::default();
  if let Some(path) = &args.file {
  if args.primary_package {
  @@ -254,6 +252,11 @@ pub fn fix_maybe_exec_rustc() -> CargoResult<bool> {
  }
  }
  + // This final fall-through handles multiple cases;
  + // - Non-primary crates, which need to be built.
  + // - If the fix failed, show the original warnings and suggestions.
  + // - If `--broken-code`, show the error messages.
  + // - If the fix succeeded, show any remaining warnings.
  let mut cmd = Command::new(&rustc);
  args.apply(&mut cmd);
  exit_with(cmd.status().context("failed to spawn rustc")?);
  