implement help menu

This appears when running pfetch-rs in a podman Arch Linux container

src/lib.rs

@@ -228,7 +228,7 @@ pub fn os(general_readout: &GeneralReadout) -> Option<String> {
                 Some("Bedrock Linux".to_string())
             } else {
                 match general_readout.distribution() {
-                    Ok(distribution) => Some(distribution),
+                    Ok(distribution) => Some(distribution.replace(" TEMPLATE_VERSION_ID", "")),
                     Err(_) => None,
                 }
             }

src/main.rs

@@ -206,6 +206,10 @@ fn main() {
     if std::env::args().any(|arg| arg.starts_with("-v") || arg.starts_with("--v")) {
         println!("pfetch-rs {}", env!("CARGO_PKG_VERSION"));
         std::process::exit(0);
+    } else if std::env::args().len() > 1 {
+        println!("pfetch     show system information");
+        println!("pfetch -v  show version");
+        std::process::exit(0);
     }
 
     // source file specified by env: PF_SOURCE