Provide a custom usage string for --help

The generated output is not very readable. We can do better by providing
a custom string. This makes the binary smaller too.

Author: keszybz

Cargo.toml

@@ -14,11 +14,12 @@ exclude = ["tests/07a-mount-point-excl", "tests/10-example"]
 
 [dependencies]
 anyhow = "1.0.12"
-clap = { version = "4.5", default-features = false, features = ["std", "cargo", "help" , "usage", "error-context"] }
+clap = { version = "4.5", default-features = false, features = ["std", "cargo", "help" , "error-context"] }
 liboverdrop = "0.1.0"
 rust-ini = ">=0.15, <0.18"
 log = { version = "0.4", features = ["std"] }
 fasteval = { version = "0.2", default-features = false }
+indoc = "2.0.5"
 
 [dev-dependencies]
 tempfile = "3"

src/main.rs

@@ -6,6 +6,7 @@ mod kernlog;
 mod setup;
 
 use anyhow::Result;
+use indoc::indoc;
 use log::{info, LevelFilter};
 use std::borrow::Cow;
 use std::env;
@@ -24,6 +25,11 @@ enum Opts {
 #[rustfmt::skip]
 fn command() -> clap::Command {
     clap::command!()
+        .override_usage(indoc! {"
+            zram-generator --setup-device <device>
+                   zram-generator --reset-device <device>
+                   zram-generator dir1 [dir2 dir3]
+        "})
         .arg(
             clap::arg!(--"setup-device" <device> "Set up a single device")
                 .conflicts_with("reset-device")