Add option to suppress trailing newline

When generating a UID within a script, it can be helpful to have it
returned without the trailing newline.  Let's add a `-n` option to
enable this.

xtask/src/main.rs

@@ -19,20 +19,21 @@ fn print_uid() {
     let mut xs = [0u8; UID_LEN];
     getrandom::getrandom(&mut xs).unwrap();
     xs.iter().for_each(|x| print!("{x:02x}"));
-    println!();
 }
 
-fn print_usage() {
+fn print_usage() -> ExitCode {
     const USAGE: &str = "\
-Usage: cargo xtask [OPTIONS] COMMAND
+Usage: cargo xtask [OPTIONS] COMMAND [COMMAND_OPTIONS]
 
 Commands:
   generate-uid, uid    Generate an event UID
+    -n                 Suppress trailing newline
 
 Options:
   -h                   Print help
 ";
     println!("{USAGE}");
+    ExitCode::SUCCESS
 }
 
 fn err_usage() -> ExitCode {
@@ -44,10 +45,21 @@ fn main() -> ExitCode {
     let mut args = std::env::args();
     let _arg0 = args.next().unwrap();
     let Some(arg1) = args.next() else { return err_usage() };
-    let None = args.next() else { return err_usage() };
     match &*arg1 {
-        "-h" => print_usage(),
-        "generate-uid" | "uid" => print_uid(),
+        "-h" => return print_usage(),
+        "generate-uid" | "uid" => {
+            let mut trailing_nl = true;
+            match args.next().as_deref() {
+                Some("-h") => return print_usage(),
+                Some("-n") => trailing_nl = false,
+                None => {}
+                _ => return err_usage(),
+            };
+            print_uid();
+            if trailing_nl {
+                println!();
+            }
+        }
         _ => return err_usage(),
     }
     ExitCode::SUCCESS