Add Nushell completion script generation support (#1756)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

easytier/src/lib.rs

@@ -3,7 +3,7 @@
 use std::io;
 
 use clap::Command;
-use clap_complete::Generator;
+use clap_complete::{Generator, Shell};
 
 mod arch;
 mod gateway;
@@ -30,6 +30,38 @@ mod tests;
 pub const VERSION: &str = common::constants::EASYTIER_VERSION;
 rust_i18n::i18n!("locales", fallback = "en");
 
+#[derive(clap::ValueEnum, Debug, Clone, PartialEq)]
+pub enum ShellType {
+    Bash,
+    Elvish,
+    Fish,
+    Powershell,
+    Zsh,
+    Nu,
+}
+
+impl ShellType {
+    pub fn to_shell(&self) -> Option<Shell> {
+        match self {
+            ShellType::Bash => Some(Shell::Bash),
+            ShellType::Elvish => Some(Shell::Elvish),
+            ShellType::Fish => Some(Shell::Fish),
+            ShellType::Powershell => Some(Shell::PowerShell),
+            ShellType::Zsh => Some(Shell::Zsh),
+            ShellType::Nu => None,
+        }
+    }
+}
+
 pub fn print_completions<G: Generator>(generator: G, cmd: &mut Command, bin_name: &str) {
     clap_complete::generate(generator, cmd, bin_name, &mut io::stdout());
 }
+
+pub fn print_nushell_completions(cmd: &mut Command, bin_name: &str) {
+    clap_complete::generate(
+        clap_complete_nushell::Nushell,
+        cmd,
+        bin_name,
+        &mut io::stdout(),
+    );
+}