Update to beta of clap 3 and improve arg handling

Author: fornwall

Cargo.lock

@@ -3,7 +3,6 @@ name = "rust-script"
 version = "0.7.0"
 edition = "2018"
 authors = ["Fredrik Fornwall <fredrik@fornwall.net>"]
-
 description = "Command-line tool to run Rust \"scripts\" which can make use of crates."
 homepage = "https://rust-script.org"
 documentation = "https://rust-script.org"
@@ -22,7 +21,7 @@ exclude = [
 
 [dependencies]
 crossbeam-channel = "0.5"
-clap = "2"
+clap = "3.0.0-beta.2"
 dirs-next = "2"
 env_logger = "0.8"
 lazy_static = "1"

Cargo.toml

@@ -0,0 +1,3 @@
+#!/usr/bin/env rust-script
+
+println!("hello, rust");

examples/hello-without-main.ers

@@ -0,0 +1,12 @@
+#!/usr/bin/env rust-script
+//! This is a regular crate doc comment, but it also contains a partial
+//! Cargo manifest.  Note the use of a *fenced* code block, and the
+//! `cargo` "language".
+//!
+//! ```cargo
+//! [dependencies]
+//! time = "0.1.25"
+//! ```
+fn main() {
+    println!("{}", time::now().rfc822z());
+}

examples/time-main.ers

@@ -0,0 +1,13 @@
+#!/usr/bin/env rust-script
+//! This is a regular crate doc comment, but it also contains a partial
+//! Cargo manifest.  Note the use of a *fenced* code block, and the
+//! `cargo` "language".
+//!
+//! ```cargo
+//! [dependencies]
+//! time = "0.1.25"
+//! ```
+
+use time::now;
+
+println!("{}", now().rfc822z());