feat: add help and version command line arguments

src/main.rs

@@ -3,7 +3,30 @@
 
 use cosmic_greeter::{greeter, locker};
 
+use lexopt::{Arg, Parser};
+
 fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mut parser = Parser::from_env();
+
+    // Parse the arguments
+    while let Some(arg) = parser.next()? {
+        match arg {
+            Arg::Short('h') | Arg::Long("help") => {
+                print_help(env!("CARGO_PKG_VERSION"), env!("VERGEN_GIT_SHA"));
+                return Ok(());
+            }
+            Arg::Short('v') | Arg::Long("version") => {
+                println!(
+                    "cosmic-greeter {} (git commit {})",
+                    env!("CARGO_PKG_VERSION"),
+                    env!("VERGEN_GIT_SHA")
+                );
+                return Ok(());
+            }
+            _ => {}
+        }
+    }
+
     match pwd::Passwd::current_user() {
         Some(current_user) => match current_user.name.as_str() {
             "cosmic-greeter" => greeter::main(),
@@ -12,3 +35,19 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         _ => Err("failed to determine current user".into()),
     }
 }
+
+fn print_help(version: &str, git_rev: &str) {
+    println!(
+        r#"cosmic-greeter {version} (git commit {git_rev})
+System76 <info@system76.com>
+
+Designed for the COSMIC™ desktop environment, cosmic-greeter is a libcosmic
+frontend for greetd which can be run inside of cosmic-comp.
+
+Project home page: https://github.com/pop-os/cosmic-greeter
+
+Options:
+  -h, --help     Show this message
+  -v, --version  Show the version of cosmic-greeter"#
+    );
+}