cleanup main program to support --with on all platforms.

Technically this is a breaking change as the way it communicates now looks different,
and error handling is different as well.

src/main.rs

@@ -1,34 +1,23 @@
-use std::{env, process};
+use std::env;
 
-fn main() {
-    let path_or_url = match env::args().nth(1) {
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mut args = env::args();
+    let path_or_url = match args.nth(1) {
         Some(arg) => arg,
-        None => {
-            eprintln!("usage: open <path-or-url>");
-            process::exit(1);
-        }
+        None => return Err("usage: open <path-or-url> [--with|-w program]".into()),
     };
 
-    #[cfg(not(windows))]
-    let result = match std::env::var("OPEN_WITH").ok() {
-        Some(program) => open::with(&path_or_url, program),
+    match args.next() {
+        Some(arg) if arg == "--with" || arg == "-w" => {
+            let program = args
+                .next()
+                .ok_or("--with must be followed by the program to use for opening")?;
+            open::with(&path_or_url, program)
+        }
+        Some(arg) => return Err(format!("Argument '{arg}' is invalid").into()),
         None => open::that(&path_or_url),
-    };
+    }?;
 
-    #[cfg(windows)]
-    let result = match env::args().nth(2) {
-        Some(arg) if arg == "--with" || arg == "-w" => match env::args().nth(3) {
-            Some(program) => open::with(&path_or_url, program),
-            None => open::that(&path_or_url),
-        },
-        _ => open::that(&path_or_url),
-    };
-
-    match result {
-        Ok(()) => println!("Opened '{}' successfully.", path_or_url),
-        Err(err) => {
-            eprintln!("An error occurred when opening '{}': {}", path_or_url, err);
-            process::exit(3);
-        }
-    }
+    println!("Opened '{}' successfully.", path_or_url);
+    Ok(())
 }