xtask: add completion generation

xtask/main.rs

@@ -0,0 +1,69 @@
+use std::io;
+
+use clap::{
+  CommandFactory,
+  Parser as _,
+};
+
+#[derive(clap::Parser)]
+struct Cli {
+  #[clap(subcommand)]
+  command: Command,
+}
+
+#[derive(clap::Subcommand)]
+enum Command {
+  /// Generate completions for the specified shell.
+  GenerateCompletions {
+    #[arg(long)]
+    shell: Shell,
+
+    #[arg(long)]
+    binary: Binary,
+  },
+}
+
+#[expect(clippy::enum_variant_names)]
+#[derive(clap::ValueEnum, Debug, Clone, Copy, PartialEq, Eq)]
+enum Shell {
+  Bash,
+  Elvish,
+  Fish,
+  PowerShell,
+  Zsh,
+  Nushell,
+}
+
+#[derive(clap::ValueEnum, Debug, Clone, Copy, PartialEq, Eq)]
+enum Binary {
+  Watt,
+  Cpu,
+  Power,
+}
+
+fn main() {
+  let cli = Cli::parse();
+
+  match cli.command {
+    Command::GenerateCompletions { shell, binary } => {
+      let mut command = match binary {
+        Binary::Watt => watt::WattCommand::command(),
+        Binary::Cpu => watt::CpuCommand::command(),
+        Binary::Power => watt::PowerCommand::command(),
+      };
+      command.set_bin_name(format!("{binary:?}").to_lowercase());
+      command.build();
+
+      let shell: &dyn clap_complete::Generator = match shell {
+        Shell::Bash => &clap_complete::Shell::Bash,
+        Shell::Elvish => &clap_complete::Shell::Elvish,
+        Shell::Fish => &clap_complete::Shell::Fish,
+        Shell::PowerShell => &clap_complete::Shell::PowerShell,
+        Shell::Zsh => &clap_complete::Shell::Zsh,
+        Shell::Nushell => &clap_complete_nushell::Nushell,
+      };
+
+      shell.generate(&command, &mut io::stdout());
+    },
+  }
+}