cli: add 'completions <SHELL>' subcommand via clap_complete

Cargo.lock

@@ -357,6 +357,15 @@ dependencies = [
  "strsim",
 ]
 
+[[package]]
+name = "clap_complete"
+version = "4.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "660c0520455b1013b9bcb0393d5f643d7e4454fb69c915b8d6d2aa0e9a45acc3"
+dependencies = [
+ "clap",
+]
+
 [[package]]
 name = "clap_derive"
 version = "4.6.0"
@@ -1604,6 +1613,7 @@ dependencies = [
  "assert_cmd",
  "chrono",
  "clap",
+ "clap_complete",
  "data-encoding",
  "dirs",
  "ed25519-dalek",

crates/relicario-cli/Cargo.toml

@@ -25,6 +25,7 @@ zeroize = "1"
 url = "2"
 data-encoding = "2"
 tar = { version = "0.4", default-features = false }
+clap_complete = "4"
 
 [dev-dependencies]
 assert_cmd = "2"

crates/relicario-cli/src/main.rs

@@ -8,7 +8,8 @@ mod session;
 use std::path::PathBuf;
 
 use anyhow::{bail, Context, Result};
-use clap::{Parser, Subcommand};
+use clap::{CommandFactory, Parser, Subcommand};
+use clap_complete::{generate, Shell};
 
 #[derive(Parser)]
 #[command(
@@ -163,6 +164,13 @@ enum Commands {
 
     /// Lock the vault (no-op in CLI; present for UX parity with the extension).
     Lock,
+
+    /// Emit a shell completion script for the given shell.
+    /// Pipe to your shell's completion file (e.g. `> /etc/bash_completion.d/relicario`).
+    Completions {
+        #[arg(value_enum)]
+        shell: Shell,
+    },
 }
 
 #[derive(Subcommand)]
@@ -354,6 +362,11 @@ fn main() -> Result<()> {
         Commands::Status => cmd_status(),
         Commands::Device { action } => cmd_device(action),
         Commands::Lock => { eprintln!("no cached session to lock"); Ok(()) }
+        Commands::Completions { shell } => {
+            let mut cmd = Cli::command();
+            generate(shell, &mut cmd, "relicario", &mut std::io::stdout());
+            Ok(())
+        }
     }
 }
 

crates/relicario-cli/tests/smart_inputs.rs

@@ -0,0 +1,30 @@
+use assert_cmd::Command;
+use predicates::str::contains;
+
+#[test]
+fn completions_bash_emits_script() {
+    Command::cargo_bin("relicario").unwrap()
+        .args(["completions", "bash"])
+        .assert()
+        .success()
+        .stdout(contains("_relicario"))
+        .stdout(contains("complete -F"));
+}
+
+#[test]
+fn completions_zsh_emits_script() {
+    Command::cargo_bin("relicario").unwrap()
+        .args(["completions", "zsh"])
+        .assert()
+        .success()
+        .stdout(contains("#compdef relicario"));
+}
+
+#[test]
+fn completions_fish_emits_script() {
+    Command::cargo_bin("relicario").unwrap()
+        .args(["completions", "fish"])
+        .assert()
+        .success()
+        .stdout(contains("complete -c relicario"));
+}