fix(toml): Teach users how to pin edition (#16851)

### What does this PR try to resolve?

Only when not `--quiet` (note: piped stderr implies `--quiet`)

This tries to strike a balance between
- Helping users know how to react to the warning
- Good noise that encourages users to pin the edition
- Bad noise that overwhelms the throwaway scripts

### How to test and review this PR

Author: weihanglo

src/cargo/util/toml/mod.rs

@@ -633,9 +633,14 @@ fn normalize_package_toml<'a>(
             if is_embedded {
                 const DEFAULT_EDITION: crate::core::features::Edition =
                     crate::core::features::Edition::LATEST_STABLE;
-                let report = [Group::with_title(Level::WARNING.secondary_title(format!(
+                let mut report = vec![Group::with_title(Level::WARNING.secondary_title(format!(
                     "`package.edition` is unspecified, defaulting to the latest edition (currently `{DEFAULT_EDITION}`)"
                 )))];
+                if !matches!(gctx.shell().verbosity(), cargo_util_terminal::Verbosity::Quiet) {
+                    report.push(Group::with_title(Level::HELP.secondary_title(format!(
+                        "to pin the edition, run `cargo fix --manifest-path {}`", manifest_file.display()
+                    ))));
+                }
                 let _ = gctx.shell().print_report(&report, true);
                 Some(manifest::InheritableField::Value(
                     DEFAULT_EDITION.to_string(),

tests/testsuite/cargo_add/script_bare/stderr.term.svg

@@ -3091,6 +3091,7 @@ fn script_without_frontmatter() {
         .with_stdout_data(str![""])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/echo.rs`
 [FIXED] echo.rs (1 fix)
 [CHECKING] echo v0.0.0 ([ROOT]/foo/echo.rs)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -3129,6 +3130,7 @@ fn main() {}",
         .with_stdout_data(str![""])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/echo.rs`
 [FIXED] echo.rs (1 fix)
 [CHECKING] echo v0.0.0 ([ROOT]/foo/echo.rs)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -3169,6 +3171,7 @@ fn main() {}"#,
         .with_stdout_data(str![""])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/echo.rs`
 [FIXED] echo.rs (1 fix)
 [CHECKING] foo v0.0.0 ([ROOT]/foo/echo.rs)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -3208,6 +3211,7 @@ fn main() {}"#,
         .with_stdout_data(str![""])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/echo.rs`
 [FIXED] echo.rs (1 fix)
 [CHECKING] foo v0.0.0 ([ROOT]/foo/echo.rs)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s

tests/testsuite/cargo_add/script_frontmatter_empty/stderr.term.svg

@@ -154,6 +154,7 @@ fn main() {}"#,
         .masquerade_as_nightly_cargo(&["cargo-lints", "script"])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/foo_bar`
 [WARNING] binaries should have a kebab-case name
   |
 1 | [ROOT]/home/.cargo/build/[HASH]/target/.../foo_bar[EXE]

tests/testsuite/cargo_add/script_shebang/stderr.term.svg

@@ -61,6 +61,7 @@ fn main() {}"#,
         .masquerade_as_nightly_cargo(&["cargo-lints", "script"])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/foo_bar`
 [WARNING] packages should have a kebab-case name
  --> foo_bar
   = [NOTE] `cargo::non_kebab_case_packages` is set to `warn` in `[lints]`

tests/testsuite/cargo_remove/script/stderr.term.svg

@@ -61,6 +61,7 @@ fn main() {}"#,
         .masquerade_as_nightly_cargo(&["cargo-lints", "script"])
         .with_stderr_data(str![[r#"
 [WARNING] `package.edition` is unspecified, defaulting to the latest edition (currently `[..]`)
+[HELP] to pin the edition, run `cargo fix --manifest-path [ROOT]/foo/foo-bar`
 [WARNING] packages should have a snake-case name
  --> foo-bar
   = [NOTE] `cargo::non_snake_case_packages` is set to `warn` in `[lints]`