Implement config subcommand

The synopsis is as follows.

List all top-level config keys:

    $ ruff config
    allowed-confusables
    builtins
    cache-dir
    ... etc.

List all config keys in a specific section:

    $ ruff config mccabe
    max-complexity

Describe a specific config option:

    $ ruff config mccabe.max-complexity
    The maximum McCabe complexity to allow before triggering `C901` errors.

    Default value: 10
    Type: int
    Example usage:
    ```toml
    # Flag errors (`C901`) whenever the complexity level exceeds 5.
    max-complexity = 5
    ```

crates/ruff_cli/src/args.rs

@@ -44,6 +44,8 @@ pub enum Command {
         #[arg(long, value_enum, default_value = "pretty")]
         format: HelpFormat,
     },
+    /// List or describe the available configuration options
+    Config { option: Option<String> },
     /// List all supported upstream linters
     Linter {
         /// Output format

crates/ruff_cli/src/commands/config.rs

@@ -0,0 +1,48 @@
+use ruff::settings::{
+    options::Options,
+    options_base::{ConfigurationOptions, OptionEntry, OptionField},
+};
+
+use crate::ExitStatus;
+
+#[allow(clippy::print_stdout)]
+pub(crate) fn config(option: Option<&str>) -> ExitStatus {
+    let entries = Options::get_available_options();
+    let mut entries = &entries;
+
+    let mut parts_iter = option.iter().flat_map(|s| s.split('.'));
+
+    while let Some(part) = parts_iter.next() {
+        let Some((_, field)) = entries.iter().find(|(name, _)| *name == part) else {
+            println!("Unknown option");
+            return ExitStatus::Error;
+        };
+        match field {
+            OptionEntry::Field(OptionField {
+                doc,
+                default,
+                value_type,
+                example,
+            }) => {
+                if parts_iter.next().is_some() {
+                    println!("Unknown option");
+                    return ExitStatus::Error;
+                }
+
+                println!("{doc}");
+                println!();
+                println!("Default value: {default}");
+                println!("Type: {value_type}");
+                println!("Example usage:\n```toml\n{example}\n```");
+                return ExitStatus::Success;
+            }
+            OptionEntry::Group(fields) => {
+                entries = fields;
+            }
+        }
+    }
+    for (name, _) in entries {
+        println!("{name}");
+    }
+    ExitStatus::Success
+}

crates/ruff_cli/src/commands/mod.rs

@@ -9,6 +9,7 @@ pub use show_settings::show_settings;
 
 mod add_noqa;
 mod clean;
+pub mod config;
 mod linter;
 mod rule;
 mod run;

crates/ruff_cli/src/main.rs

@@ -101,6 +101,7 @@ quoting the executed command, along with the relevant file contents and `pyproje
 
     match command {
         Command::Rule { rule, format } => commands::rule(&rule, format)?,
+        Command::Config { option } => return Ok(commands::config::config(option.as_deref())),
         Command::Linter { format } => commands::linter(format)?,
         Command::Clean => commands::clean(log_level)?,
         Command::GenerateShellCompletion { shell } => {