Add support for -h/--help arg

Signed-off-by: Haobo Gu <haobogu@outlook.com>

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+- [#102] Add support for -h/--help arg and no arg
+
+[#102]: https://github.com/knurling-rs/flip-link/pull/102
+
 ## [v0.1.9] - 2024-08-14
 
 - [#96] Add support for @file args

src/main.rs

@@ -29,6 +29,24 @@ fn notmain() -> Result<i32> {
     // NOTE `skip` the name/path of the binary (first argument)
     let raw_args = env::args().skip(1).collect::<Vec<_>>();
 
+    // If there's no argument provided, print the help message
+    if matches!(
+        raw_args
+            .iter()
+            .map(|s| s.as_str())
+            .collect::<Vec<&str>>()
+            .as_slice(),
+        [] | ["--help"] | ["-h"]
+    ) {
+        eprintln!(
+            "flip-link: adds zero-cost stack overflow protection to your \
+            embedded programs\nYou should not use flip-link directly from \
+            command line, use flip-link as your default linker instead. \n\n\
+            For detailed usage, check https://github.com/knurling-rs/flip-link"
+        );
+        return Ok(0);
+    }
+
     {
         let exit_status = linking::link_normally(&raw_args)?;
         if !exit_status.success() {