Add shell completions

- Add a `build.rs` (plus dependencies) to generate the shell completions
  clap knows.

Cargo.lock

@@ -326,6 +326,15 @@ dependencies = [
  "strsim",
 ]
 
+[[package]]
+name = "clap_complete"
+version = "4.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e0a7a9bfdb35811f9e59832f0f05975114d2251b415fb534108e6f34060fd772"
+dependencies = [
+ "clap",
+]
+
 [[package]]
 name = "clap_derive"
 version = "4.6.1"
@@ -1028,6 +1037,8 @@ dependencies = [
  "anyhow",
  "bytes",
  "clap",
+ "clap_complete",
+ "fastrand",
  "indymilter",
  "log",
  "log4rs",

Cargo.toml

@@ -15,6 +15,7 @@ aho-corasick = "1.1.4"
 anyhow = "1.0.100"
 bytes = "1.11.1"
 clap = { version = "4", features = ["derive"] }
+fastrand = "2.4.1"
 indymilter = "0.3.0"
 log = "0.4.30"
 log4rs = "1.3.0"
@@ -28,3 +29,8 @@ serde_derive = "1.0.228"
 thiserror = "2.0.17"
 tokio = { version = "1.52.3", features = [ "tokio-macros", "rt-multi-thread", "signal" ] }
 toml = "0.9.8"
+
+[build-dependencies]
+anyhow = "1.0.100"
+clap = { version = "4", features = ["derive"] }
+clap_complete = "4"

build.rs

@@ -0,0 +1,50 @@
+//! build
+
+use anyhow::Result;
+use anyhow;
+use clap::CommandFactory;
+use clap::ValueEnum;
+use clap_complete::Shell;
+
+use std::env;
+use std::fs;
+use std::path::PathBuf;
+
+// include the cli definition
+pub mod cli {
+    include!("src/cli/cli_args.rs");
+}
+
+const ASSET_OUT_ENV_NAME: &str = "ASSET_OUT_DIR";
+
+/// Returns a path to a directory suitable as a target for generated
+/// files.
+fn out_dir(section: &str) -> Result<PathBuf> {
+    println!("cargo:rerun-if-env-changed={}", ASSET_OUT_ENV_NAME);
+
+    let outdir: PathBuf = env::var_os(ASSET_OUT_ENV_NAME)
+        .unwrap_or_else(|| env::var_os("OUT_DIR")
+            .expect("OUT_DIR not set")
+        ).into();
+
+    if outdir.exists() && ! outdir.is_dir() {
+        return Err(anyhow::anyhow!("{:?} is not a directory", outdir));
+    }
+    let path = outdir.join(section);
+    fs::create_dir_all(&path)?;
+    Ok(path)
+}
+
+fn main() -> Result<()> {
+    let mut husk = cli::CliArgs::command();
+
+    // shell completions
+    let shell_completion_path = out_dir("shell_completions")?;
+    for shell in Shell::value_variants() {
+        clap_complete::generate_to(*shell, &mut husk, "husk", &shell_completion_path)?;
+    }
+
+    println!("cargo:warning=shell completions written to {}", shell_completion_path.display());
+
+    Ok(())
+}