Don't panic on wrong argument, instead display error message

src/main.rs

@@ -1,5 +1,6 @@
 use std::env::{set_current_dir as cd, set_var};
 use structopt::StructOpt;
+use structopt::clap::ErrorKind as ClapError;
 // For UNIX extended metadata
 
 mod cli;
@@ -11,11 +12,27 @@ mod task;
 use log::Context;
 
 fn main() -> Result<(), std::io::Error> {
+    let mut context = Context::new();
+
     // TODO: use StructOpt::from_iter_safe so we can hook on Cli error
     // to display additional unknown_arg error message.
-    let cmd = cli::Cli::from_args();
-
-    let mut context = Context::new();
+    //let cmd = cli::Cli::from_args();
+    let res = cli::Cli::from_iter_safe(std::env::args());
+    if res.is_err() {
+        let e = res.unwrap_err();
+        match &e.kind {
+            ClapError::UnknownArgument => {
+                context.insert("$i18n_arg".to_string(), e.info.unwrap().first().unwrap().to_string());
+                log::error("unknown_arg", &context);
+                std::process::exit(1);
+            },
+            /*ClapError::HelpDisplayed {
+                e.exit()
+            }*/
+            _ => e.exit()
+        }
+    }
+    let cmd = res.unwrap();
 
     let basedir = cmd.basedir();
     context.insert("$i18n_basedir".to_string(), basedir.to_str().unwrap().to_string());