cli: migrate from gumdrop to clap v3 (#379)

`gumdrop` was originally chosen for its minimalist set of dependencies,
but `clap` v3 has a slimmed down set of dependencies and better UX.

cli/src/commands.rs

@@ -4,62 +4,25 @@ pub mod readers;
 pub mod status;
 
 use self::{readers::ReadersCmd, status::StatusCmd};
-use crate::terminal::{self, STDOUT};
-use gumdrop::Options;
-use std::{
-    env,
-    io::{self, Write},
-    process::exit,
-};
-use termcolor::{ColorChoice, ColorSpec, WriteColor};
+use crate::terminal;
+use clap::Parser;
+use std::{env, process::exit};
+use termcolor::ColorChoice;
 use yubikey::{Serial, YubiKey};
 
 /// The `yubikey` CLI utility
-#[derive(Debug, Options)]
+#[derive(Debug, Parser)]
 pub struct YubiKeyCli {
-    /// Obtain help about the current command
-    #[options(short = "h", help = "print help message")]
-    pub help: bool,
-
-    /// Specify the serial number of the YubiKey to connect to
-    #[options(
-        short = "s",
-        long = "serial",
-        help = "serial number of the YubiKey to connect to"
-    )]
+    /// Serial number of the YubiKey to connect to
+    #[clap(short = 's', long = "serial")]
     pub serial: Option<Serial>,
 
     /// Subcommand to execute.
-    #[options(command)]
-    pub command: Option<Commands>,
+    #[clap(subcommand)]
+    pub command: Commands,
 }
 
 impl YubiKeyCli {
-    /// Print usage information
-    pub fn print_usage() -> io::Result<()> {
-        let mut stdout = STDOUT.lock();
-        stdout.reset()?;
-
-        let mut bold = ColorSpec::new();
-        bold.set_bold(true);
-
-        stdout.set_color(&bold)?;
-        writeln!(
-            stdout,
-            "{} {}",
-            env!("CARGO_PKG_NAME"),
-            env!("CARGO_PKG_VERSION")
-        )?;
-        stdout.reset()?;
-
-        writeln!(stdout, "{}", env!("CARGO_PKG_AUTHORS"))?;
-        writeln!(stdout, "{}", env!("CARGO_PKG_DESCRIPTION").trim())?;
-        writeln!(stdout)?;
-        writeln!(stdout, "{}", Commands::usage())?;
-
-        Ok(())
-    }
-
     /// Run the underlying command type or print usage info and exit
     pub fn run(&self) {
         // TODO(tarcieri): make this more configurable
@@ -70,10 +33,7 @@ impl YubiKeyCli {
             env_logger::builder().format_timestamp(None).init();
         }
 
-        match &self.command {
-            Some(cmd) => cmd.run(self.yubikey_init()),
-            None => Self::print_usage().unwrap(),
-        }
+        self.command.run(self.yubikey_init())
     }
 
     /// Initialize the YubiKey client driver
@@ -92,22 +52,18 @@ impl YubiKeyCli {
 }
 
 /// Subcommands of this application
-#[derive(Debug, Options)]
+#[derive(Debug, Parser)]
 pub enum Commands {
-    /// `help` subcommand
-    #[options(help = "show help for a command")]
-    Help(HelpOpts),
-
     /// `version` subcommand
-    #[options(help = "display version information")]
+    #[clap(about = "display version information")]
     Version(VersionOpts),
 
     /// `readers` subcommand
-    #[options(help = "list detected readers")]
+    #[clap(about = "list detected readers")]
     Readers(ReadersCmd),
 
     /// `status` subcommand
-    #[options(help = "show yubikey status")]
+    #[clap(about = "show yubikey status")]
     Status(StatusCmd),
 }
 
@@ -115,7 +71,6 @@ impl Commands {
     /// Run the given command
     pub fn run(&self, yubikey: YubiKey) {
         match self {
-            Commands::Help(help) => help.run(),
             Commands::Version(version) => version.run(),
             Commands::Readers(list) => list.run(),
             Commands::Status(status) => status.run(yubikey),
@@ -123,28 +78,8 @@ impl Commands {
     }
 }
 
-/// Help options
-#[derive(Debug, Options)]
-pub struct HelpOpts {
-    #[options(free, help = "subcommand to get help for")]
-    free: Vec<String>,
-}
-
-impl HelpOpts {
-    fn run(&self) {
-        if let Some(command) = self.free.first() {
-            if let Some(usage) = Commands::command_usage(command) {
-                println!("{}", usage);
-                exit(1);
-            }
-        }
-
-        println!("{}", Commands::usage());
-    }
-}
-
 /// Version options
-#[derive(Debug, Options)]
+#[derive(Debug, Parser)]
 pub struct VersionOpts {}
 
 impl VersionOpts {