add shell completion script generation

src/cmd_args.rs

@@ -55,6 +55,11 @@ pub(crate) enum Commands {
 
     /// Check config files.
     Check {},
+
+    /// Generate completion script.
+    Completion {
+        shell: clap_complete::Shell,
+    }
 }
 
 #[derive(Args, Debug)]

src/cmd_completion.rs

@@ -0,0 +1,12 @@
+use crate::cmd_args::Cli;
+use std::io;
+
+use anyhow::Result;
+use clap::CommandFactory;
+use clap_complete::Shell;
+
+pub(crate) fn cmd_completion(shell: Shell) -> Result<()> {
+    let mut cmd = Cli::command();
+    clap_complete::generate(shell, &mut cmd, "xdbm", &mut io::stdout());
+    Ok(())
+}

src/main.rs

@@ -31,6 +31,7 @@ mod cmd_backup;
 mod cmd_init;
 mod cmd_storage;
 mod cmd_sync;
+mod cmd_completion;
 mod devices;
 mod inquire_filepath_completer;
 mod storages;
@@ -122,6 +123,9 @@ fn main() -> Result<()> {
                 } => cmd_backup::cmd_backup_done(name, exit_status, log, repo, &config_dir)?,
             }
         }
+        Commands::Completion { shell } => {
+            cmd_completion::cmd_completion(shell)?
+        }
     }
     full_status(&Repository::open(&config_dir)?)?;
     Ok(())