feat: register works

src/sign.rs

@@ -0,0 +1,14 @@
+use clap::{ArgMatches, SubCommand, App};
+use crate::cmd::{Command, CommandError};
+
+pub struct CommandImpl;
+
+impl Command for CommandImpl {
+    fn name(&self) -> &str { "sign" }
+    fn subcommand<'a>(&self) -> App<'a, 'a> {
+        SubCommand::with_name(self.name()).about("Sign subcommand")
+    }
+    fn run(&self, _arg_matches: &ArgMatches, _sub_arg_matches: &ArgMatches) -> CommandError {
+        Ok(())
+    }
+}