added cli interface options and some error msgs

src/cli/mod.rs

@@ -0,0 +1,13 @@
+use clap::{Parser, Subcommand};
+
+#[derive(Parser, Debug)]
+#[command(version, about)]
+pub struct Args {
+    /// set config file to use
+    #[arg(short, long, value_name = "FILE")]
+    pub config: Option<String>,
+
+    /// show current config file
+    #[arg(short = 'C', long)]
+    pub current_config: bool,
+}