Add help headings matching cargo rustc --help

src/main.rs

@@ -261,32 +261,28 @@ fn apply_args(cmd: &mut Command, args: &Expand, color: &Coloring, outfile: &Path
 
     line.arg("rustc");
 
-    line.arg("--profile");
-    if let Some(profile) = &args.profile {
-        line.arg(profile);
-    } else if args.tests && args.test.is_none() {
-        if args.release {
-            line.arg("bench");
-        } else {
-            line.arg("test");
-        }
-    } else if args.release {
-        line.arg("release");
-    } else {
-        line.arg("check");
+    if args.verbose {
+        line.arg("--verbose");
     }
 
-    if let Some(features) = &args.features {
-        line.arg("--features");
-        line.arg(features);
+    line.arg("--color");
+    match color {
+        Coloring::Auto => line.arg(if cfg!(not(windows)) && io::stderr().is_terminal() {
+            "always"
+        } else {
+            "never"
+        }),
+        color => line.arg(color.to_possible_value().unwrap().get_name()),
     }
 
-    if args.all_features {
-        line.arg("--all-features");
+    for unstable_flag in &args.unstable_flags {
+        line.arg("-Z");
+        line.arg(unstable_flag);
     }
 
-    if args.no_default_features {
-        line.arg("--no-default-features");
+    if let Some(package) = &args.package {
+        line.arg("--package");
+        line.args(package);
     }
 
     let mut has_explicit_build_target = false;
@@ -330,43 +326,52 @@ fn apply_args(cmd: &mut Command, args: &Expand, color: &Coloring, outfile: &Path
         }
     }
 
-    if let Some(target) = &args.target {
-        line.arg("--target");
-        line.arg(target);
-    }
-
-    if let Some(target_dir) = &args.target_dir {
-        line.arg("--target-dir");
-        line.arg(target_dir);
+    if let Some(features) = &args.features {
+        line.arg("--features");
+        line.arg(features);
     }
 
-    if let Some(manifest_path) = &args.manifest_path {
-        line.arg("--manifest-path");
-        line.arg(manifest_path);
+    if args.all_features {
+        line.arg("--all-features");
     }
 
-    if let Some(package) = &args.package {
-        line.arg("--package");
-        line.args(package);
+    if args.no_default_features {
+        line.arg("--no-default-features");
     }
 
     if let Some(jobs) = args.jobs {
         line.arg("--jobs");
         line.arg(jobs.to_string());
     }
 
-    if args.verbose {
-        line.arg("--verbose");
+    line.arg("--profile");
+    if let Some(profile) = &args.profile {
+        line.arg(profile);
+    } else if args.tests && args.test.is_none() {
+        if args.release {
+            line.arg("bench");
+        } else {
+            line.arg("test");
+        }
+    } else if args.release {
+        line.arg("release");
+    } else {
+        line.arg("check");
     }
 
-    line.arg("--color");
-    match color {
-        Coloring::Auto => line.arg(if cfg!(not(windows)) && io::stderr().is_terminal() {
-            "always"
-        } else {
-            "never"
-        }),
-        color => line.arg(color.to_possible_value().unwrap().get_name()),
+    if let Some(target) = &args.target {
+        line.arg("--target");
+        line.arg(target);
+    }
+
+    if let Some(target_dir) = &args.target_dir {
+        line.arg("--target-dir");
+        line.arg(target_dir);
+    }
+
+    if let Some(manifest_path) = &args.manifest_path {
+        line.arg("--manifest-path");
+        line.arg(manifest_path);
     }
 
     if args.frozen {
@@ -381,11 +386,6 @@ fn apply_args(cmd: &mut Command, args: &Expand, color: &Coloring, outfile: &Path
         line.arg("--offline");
     }
 
-    for unstable_flag in &args.unstable_flags {
-        line.arg("-Z");
-        line.arg(unstable_flag);
-    }
-
     line.arg("--");
 
     line.arg("-o");

src/opts.rs

@@ -3,6 +3,13 @@ use std::path::PathBuf;
 use std::str::FromStr;
 use syn_select::Selector;
 
+// Help headings
+const PACKAGE_SELECTION: &str = "Package Selection";
+const TARGET_SELECTION: &str = "Target Selection";
+const FEATURE_SELECTION: &str = "Feature Selection";
+const COMPILATION_OPTIONS: &str = "Compilation Options";
+const MANIFEST_OPTIONS: &str = "Manifest Options";
+
 #[derive(Parser)]
 #[command(bin_name = "cargo", version, author, disable_help_subcommand = true)]
 pub enum Subcommand {
@@ -13,113 +20,113 @@ pub enum Subcommand {
 
 #[derive(Parser, Debug)]
 pub struct Expand {
-    /// Space-separated list of features to activate
-    #[arg(long, value_name = "FEATURES")]
-    pub features: Option<String>,
+    /// Do not attempt to run rustfmt
+    #[arg(long)]
+    pub ugly: bool,
 
-    /// Activate all available features
+    /// Select syntax highlighting theme
+    #[arg(long, value_name = "NAME")]
+    pub theme: Option<String>,
+
+    /// Print available syntax highlighting theme names
     #[arg(long)]
-    pub all_features: bool,
+    pub themes: bool,
 
-    /// Do not activate the `default` feature
+    /// Print command lines as they are executed
     #[arg(long)]
-    pub no_default_features: bool,
+    pub verbose: bool,
 
-    /// Expand only this package's library
+    /// Coloring: auto, always, never
+    #[arg(long, value_name = "WHEN")]
+    pub color: Option<Coloring>,
+
+    /// Unstable (nightly-only) flags to Cargo
+    #[arg(short = 'Z', value_name = "FLAG")]
+    pub unstable_flags: Vec<String>,
+
+    /// Print version
     #[arg(long)]
+    pub version: bool,
+
+    /// Package to expand
+    #[arg(short, long, value_name = "SPEC", num_args = 0..=1, help_heading = PACKAGE_SELECTION)]
+    pub package: Option<Option<String>>,
+
+    /// Expand only this package's library
+    #[arg(long, help_heading = TARGET_SELECTION)]
     pub lib: bool,
 
     /// Expand only the specified binary
-    #[arg(long, value_name = "NAME", num_args = 0..=1)]
+    #[arg(long, value_name = "NAME", num_args = 0..=1, help_heading = TARGET_SELECTION)]
     pub bin: Option<Option<String>>,
 
     /// Expand only the specified example
-    #[arg(long, value_name = "NAME", num_args = 0..=1)]
+    #[arg(long, value_name = "NAME", num_args = 0..=1, help_heading = TARGET_SELECTION)]
     pub example: Option<Option<String>>,
 
     /// Expand only the specified test target
-    #[arg(long, value_name = "NAME", num_args = 0..=1)]
+    #[arg(long, value_name = "NAME", num_args = 0..=1, help_heading = TARGET_SELECTION)]
     pub test: Option<Option<String>>,
 
     /// Include tests when expanding the lib or bin
-    #[arg(long)]
+    #[arg(long, help_heading = TARGET_SELECTION)]
     pub tests: bool,
 
     /// Expand only the specified bench target
-    #[arg(long, value_name = "NAME", num_args = 0..=1)]
+    #[arg(long, value_name = "NAME", num_args = 0..=1, help_heading = TARGET_SELECTION)]
     pub bench: Option<Option<String>>,
 
-    /// Target triple which compiles will be for
-    #[arg(long, value_name = "TARGET")]
-    pub target: Option<String>,
+    /// Space-separated list of features to activate
+    #[arg(long, value_name = "FEATURES", help_heading = FEATURE_SELECTION)]
+    pub features: Option<String>,
 
-    /// Directory for all generated artifacts
-    #[arg(long, value_name = "DIRECTORY")]
-    pub target_dir: Option<PathBuf>,
+    /// Activate all available features
+    #[arg(long, help_heading = FEATURE_SELECTION)]
+    pub all_features: bool,
 
-    /// Path to Cargo.toml
-    #[arg(long, value_name = "PATH")]
-    pub manifest_path: Option<PathBuf>,
+    /// Do not activate the `default` feature
+    #[arg(long, help_heading = FEATURE_SELECTION)]
+    pub no_default_features: bool,
 
-    /// Package to expand
-    #[arg(short, long, value_name = "SPEC", num_args = 0..=1)]
-    pub package: Option<Option<String>>,
+    /// Number of parallel jobs, defaults to # of CPUs
+    #[arg(short, long, value_name = "N", help_heading = COMPILATION_OPTIONS)]
+    pub jobs: Option<u64>,
 
     /// Build artifacts in release mode, with optimizations
-    #[arg(long)]
+    #[arg(long, help_heading = COMPILATION_OPTIONS)]
     pub release: bool,
 
     /// Build artifacts with the specified profile
-    #[arg(long, value_name = "PROFILE-NAME")]
+    #[arg(long, value_name = "PROFILE-NAME", help_heading = COMPILATION_OPTIONS)]
     pub profile: Option<String>,
 
-    /// Number of parallel jobs, defaults to # of CPUs
-    #[arg(short, long, value_name = "N")]
-    pub jobs: Option<u64>,
+    /// Target triple which compiles will be for
+    #[arg(long, value_name = "TARGET", help_heading = COMPILATION_OPTIONS)]
+    pub target: Option<String>,
 
-    /// Print command lines as they are executed
-    #[arg(long)]
-    pub verbose: bool,
+    /// Directory for all generated artifacts
+    #[arg(long, value_name = "DIRECTORY", help_heading = COMPILATION_OPTIONS)]
+    pub target_dir: Option<PathBuf>,
 
-    /// Coloring: auto, always, never
-    #[arg(long, value_name = "WHEN")]
-    pub color: Option<Coloring>,
+    /// Path to Cargo.toml
+    #[arg(long, value_name = "PATH", help_heading = MANIFEST_OPTIONS)]
+    pub manifest_path: Option<PathBuf>,
 
     /// Require Cargo.lock and cache are up to date
-    #[arg(long)]
+    #[arg(long, help_heading = MANIFEST_OPTIONS)]
     pub frozen: bool,
 
     /// Require Cargo.lock is up to date
-    #[arg(long)]
+    #[arg(long, help_heading = MANIFEST_OPTIONS)]
     pub locked: bool,
 
     /// Run without accessing the network
-    #[arg(long)]
+    #[arg(long, help_heading = MANIFEST_OPTIONS)]
     pub offline: bool,
 
-    /// Unstable (nightly-only) flags to Cargo
-    #[arg(short = 'Z', value_name = "FLAG")]
-    pub unstable_flags: Vec<String>,
-
-    /// Do not attempt to run rustfmt
-    #[arg(long)]
-    pub ugly: bool,
-
-    /// Select syntax highlighting theme
-    #[arg(long, value_name = "NAME")]
-    pub theme: Option<String>,
-
-    /// Print available syntax highlighting theme names
-    #[arg(long)]
-    pub themes: bool,
-
     /// Local path to module or other named item to expand, e.g. os::unix::ffi
     #[arg(value_name = "ITEM", value_parser = parse_selector)]
     pub item: Option<Selector>,
-
-    /// Print version
-    #[arg(long)]
-    pub version: bool,
 }
 
 #[derive(ValueEnum, Debug, Clone, Copy)]