feat: command default print help

src/cli/app.yml

@@ -2,6 +2,8 @@ name: ckb
 author: Nervos Core Dev <dev@nervos.org>
 about: Nervos CKB - The Common Knowledge Base
 
+settings:
+    - ArgRequiredElseHelp
 subcommands:
     - run:
         about: Running ckb node
@@ -78,6 +80,8 @@ subcommands:
                 required: true
     - cli:
         about: Running ckb cli
+        settings:
+            - ArgRequiredElseHelp
         subcommands:
             - sign:
                 about: Sign transaction using sha3-secp256k1 defined in system cell

src/main.rs

@@ -36,10 +36,11 @@ mod cli;
 mod helper;
 mod setup;
 
+use build_info::Version;
 use setup::Setup;
+
 pub const DEFAULT_CONFIG_FILENAME: &str = "config.json";
 pub const DEFAULT_CONFIG: &str = include_str!("config/default.json");
-use build_info::Version;
 
 fn main() {
     // Always print backtrace on panic.
@@ -63,14 +64,14 @@ fn main() {
                 Err(e) => println!("Failed to setup, cause err {}", e.description()),
             },
             ("keygen", _) => cli::keygen(),
-            _ => println!("Invalid client subcommand"),
+            _ => unreachable!(),
         },
         ("run", Some(run_matches)) => match Setup::new(&run_matches) {
             Ok(setup) => cli::run(setup),
             Err(e) => println!("Failed to setup, cause err {}", e.description()),
         },
         ("export", Some(export_matches)) => cli::export(&export_matches),
         ("import", Some(import_matches)) => cli::import(&import_matches),
-        _ => println!("Invalid subcommand"),
+        _ => unreachable!(),
     }
 }