feat(cli): Support for tab completion

src/args.rs

@@ -15,6 +15,7 @@ pub enum Command {
         setting = structopt::clap::AppSettings::DontCollapseArgsInUsage
     )]
     Release(ReleaseOpt),
+    Completions(CompletionsOpt),
 }
 
 #[derive(Debug, StructOpt)]
@@ -222,3 +223,9 @@ fn resolve_bool_arg(yes: bool, no: bool) -> Option<bool> {
         (_, _) => unreachable!("StructOpt should make this impossible"),
     }
 }
+
+#[derive(StructOpt, Debug, Clone)]
+pub struct CompletionsOpt {
+    #[structopt(long, short = "s", possible_values = &clap::Shell::variants(), case_insensitive = true)]
+    pub shell: clap::Shell,
+}

src/main.rs

@@ -4,7 +4,7 @@
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::ffi::OsStr;
-use std::io::Write;
+use std::io::{self, Write};
 use std::path::Path;
 use std::process::exit;
 
@@ -27,16 +27,25 @@ use crate::replace::{do_file_replacements, Template};
 use crate::version::VersionExt;
 
 fn main() {
-    let args::Command::Release(ref release_matches) = args::Command::from_args();
-
-    let mut builder = get_logging(release_matches.logging.log_level());
-    builder.init();
-
-    match release_workspace(release_matches) {
-        Ok(code) => exit(code),
-        Err(e) => {
-            log::error!("Fatal: {}", e);
-            exit(128);
+    match args::Command::from_args() {
+        args::Command::Release(ref release_matches) => {
+            let mut builder = get_logging(release_matches.logging.log_level());
+            builder.init();
+
+            match release_workspace(release_matches) {
+                Ok(code) => exit(code),
+                Err(e) => {
+                    log::error!("Fatal: {}", e);
+                    exit(128);
+                }
+            }
+        }
+        args::Command::Completions(ref completion_matches) => {
+            args::Command::clap().gen_completions_to(
+                "cargo-release",
+                completion_matches.shell,
+                &mut io::stdout(),
+            );
         }
     }
 }