feat: add build time completion generation

build.rs

@@ -0,0 +1,28 @@
+#[allow(dead_code)]
+#[path = "src/model.rs"]
+mod model;
+
+include!("src/cli.rs");
+
+use clap::{CommandFactory, ValueEnum};
+use clap_complete::{generate_to, Shell};
+use std::{env, io::Error};
+
+fn main() -> Result<(), Error> {
+    let outdir = env::var_os("SHELL_COMPLETIONS_DIR")
+        .or_else(|| env::var_os("OUT_DIR"));
+
+    let Some(outdir) = outdir else {
+        return Ok(());
+    };
+
+    let mut cmd = Cli::command();
+
+    for shell in Shell::value_variants() {
+        let path = generate_to(*shell, &mut cmd, "todo", &outdir)?;
+
+        println!("cargo:warning=completion file is generated: {path:?}");
+    }
+
+    Ok(())
+}