Add completion command (#33)

This PR adds `completion` command to generate shell completion for Bash, zsh, and other shell types.

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "humble-cli"
 authors = ["Mohammad Banisaeid <[email protected]>"]
-version = "0.13.1"
+version = "0.14.0"
 license = "MIT"
 description = "The missing CLI for downloading your Humble Bundle purchases"
 documentation = "https://github.com/smbl64/humble-cli"
@@ -26,6 +26,7 @@ anyhow = "1.0"
 byte-unit = { version = "4.0", default-features = false }
 chrono = { version = "0.4", features = ["serde"] }
 clap = { version = "3.1", features = ["cargo", "derive"] }
+clap_complete = "3.2"
 dirs = "4.0.0"
 futures-util = "0.3"
 indicatif = "0.16"

README.md

@@ -36,7 +36,8 @@ Use `humble-cli auth "<YOUR SESSION KEY>"` to store the authentication key local
 After that you will have access to the following sub-commands:
 
 ```
-$ humble-cli 0.13.1
+$ humble-cli --help
+humble-cli 0.14.0
 The missing Humble Bundle CLI
 
 USAGE:
@@ -48,6 +49,7 @@ OPTIONS:
 
 SUBCOMMANDS:
     auth            Set the authentication session key
+    completion      Generate shell completions
     details         Print details of a certain bundle [aliases: info]
     download        Selectively download items from a bundle [aliases: d]
     help            Print this message or the help of the given subcommand(s)

src/main.rs

@@ -1,5 +1,8 @@
+use std::io;
+
 use anyhow::Context;
 use clap::{builder::ValueParser, value_parser, Arg, Command};
+use clap_complete::Shell;
 use humble_cli::prelude::*;
 
 fn main() {
@@ -44,6 +47,17 @@ fn run() -> Result<(), anyhow::Error> {
             )
     );
 
+    let completion_subcommand = Command::new("completion")
+        .about("Generate shell completions")
+        .arg(
+            Arg::new("SHELL")
+                .help("Shell type to generate completions for")
+                .possible_values(&["bash", "elvish", "fish", "powershell", "zsh"])
+                .takes_value(true)
+                .required(true)
+                .value_parser(value_parser!(Shell)),
+        );
+
     let list_choices_subcommand = Command::new("list-choices")
         .about("List your current Humble Choices")
         .arg(
@@ -164,20 +178,28 @@ fn run() -> Result<(), anyhow::Error> {
         details_subcommand,
         download_subcommand,
         search_subcommand,
+        completion_subcommand,
     ];
 
     let crate_name = clap::crate_name!();
 
-    let matches = clap::Command::new(crate_name)
+    let mut root = clap::Command::new(crate_name)
         .about("The missing Humble Bundle CLI")
         .version(clap::crate_version!())
         .after_help("Note: `humble-cli -h` prints a short and concise overview while `humble-cli --help` gives all details.")
         .subcommand_required(true)
         .arg_required_else_help(true)
-        .subcommands(sub_commands)
-        .get_matches();
+        .subcommands(sub_commands);
 
+    let matches = root.clone().get_matches();
     return match matches.subcommand() {
+        Some(("completion", sub_matches)) => {
+            if let Some(g) = sub_matches.get_one::<Shell>("SHELL").copied() {
+                let crate_name = clap::crate_name!();
+                clap_complete::generate(g, &mut root, crate_name, &mut io::stdout());
+            }
+            Ok(())
+        }
         Some(("auth", sub_matches)) => {
             let session_key = sub_matches.value_of("SESSION-KEY").unwrap();
             auth(session_key)