Add shell completion (#251)

* add commandline argument to generate shell completion

* update changelog

* fixup! add commandline argument to generate shell completion

* Update option name and description

---------

Co-authored-by: David Peter <mail@david-peter.de>

CHANGELOG.md

@@ -1,6 +1,7 @@
 # unreleased 
 
 - Fix memory allocation bug when terminal width is less than 10, see #244 (@selfup)
+- Add command line argument to generate shell completion, see #155 (@friedz)
 
 ## Features
 

Cargo.lock

@@ -128,6 +128,15 @@ dependencies = [
  "terminal_size",
 ]
 
+[[package]]
+name = "clap_complete"
+version = "4.5.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5abde44486daf70c5be8b8f8f1b66c49f86236edf6fa2abadb4d961c4c6229a"
+dependencies = [
+ "clap",
+]
+
 [[package]]
 name = "clap_derive"
 version = "4.5.18"
@@ -222,6 +231,7 @@ dependencies = [
  "anyhow",
  "assert_cmd",
  "clap",
+ "clap_complete",
  "const_format",
  "libc",
  "owo-colors",

Cargo.toml

@@ -19,6 +19,7 @@ owo-colors = "4"
 supports-color = "3"
 thiserror = "1.0"
 terminal_size = "0.4"
+clap_complete = "4"
 
 [dependencies.clap]
 version = "4"

src/main.rs

@@ -4,7 +4,8 @@ use std::num::{NonZeroI64, NonZeroU64};
 use std::path::PathBuf;
 
 use clap::builder::ArgPredicate;
-use clap::{ArgAction, Parser, ValueEnum};
+use clap::{ArgAction, CommandFactory, Parser, ValueEnum};
+use clap_complete::aot::{generate, Shell};
 
 use anyhow::{anyhow, bail, Context, Result};
 
@@ -192,6 +193,10 @@ struct Opt {
     /// Print a table showing how different types of bytes are colored.
     #[arg(long)]
     print_color_table: bool,
+
+    /// Show shell completion for a certain shell
+    #[arg(long, value_name("SHELL"))]
+    completion: Option<Shell>,
 }
 
 #[derive(Clone, Debug, Default, ValueEnum)]
@@ -248,6 +253,13 @@ fn run() -> Result<()> {
         return print_color_table().map_err(|e| anyhow!(e));
     }
 
+    if let Some(sh) = opt.completion {
+        let mut cmd = Opt::command();
+        let name = cmd.get_name().to_string();
+        generate(sh, &mut cmd, name, &mut io::stdout());
+        return Ok(());
+    }
+
     let stdin = io::stdin();
 
     let mut reader = match opt.file {