Add build script for man generation

Cargo.lock

@@ -134,6 +134,16 @@ version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2da6da31387c7e4ef160ffab6d5e7f00c42626fe39aea70a7b0f1773f7dd6c1b"
 
+[[package]]
+name = "clap_mangen"
+version = "0.2.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1dd95b5ebb5c1c54581dd6346f3ed6a79a3eef95dd372fc2ac13d535535300e"
+dependencies = [
+ "clap",
+ "roff",
+]
+
 [[package]]
 name = "color_quant"
 version = "1.1.0"
@@ -455,6 +465,7 @@ version = "9.0.0"
 dependencies = [
  "bitvec",
  "clap",
+ "clap_mangen",
  "crossbeam-channel",
  "env_logger",
  "filetime",
@@ -529,6 +540,12 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "roff"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b833d8d034ea094b1ea68aa6d5c740e0d04bad9d16568d08ba6f76823a114316"
+
 [[package]]
 name = "rustc-hash"
 version = "1.1.0"

Cargo.toml

@@ -78,6 +78,8 @@ features = ["png"]
 version = "0.24.6"
 
 [build-dependencies]
+clap = "4.3.8"
+clap_mangen = "0.2.20"
 rustc_version = "0.4.0"
 
 [features]

build.rs

@@ -0,0 +1,35 @@
+use clap_mangen::Man;
+use std::{env, fs::File, io::Error, path::Path};
+
+include!("src/cli.rs");
+
+fn build_manpages(outdir: &Path) -> Result<(), Error> {
+    let app = build_command();
+
+    let file = Path::new(&outdir).join("oxipng.1");
+    let mut file = File::create(file)?;
+
+    Man::new(app).render(&mut file)?;
+
+    Ok(())
+}
+
+fn main() -> Result<(), Error> {
+    println!("cargo:rerun-if-changed=src/cli.rs");
+    println!("cargo:rerun-if-changed=man");
+
+    let outdir = match env::var_os("OUT_DIR") {
+        None => return Ok(()),
+        Some(outdir) => outdir,
+    };
+
+    // Create `target/assets/` folder.
+    let out_path = PathBuf::from(outdir);
+    let mut path = out_path.ancestors().nth(4).unwrap().to_owned();
+    path.push("assets");
+    std::fs::create_dir_all(&path).unwrap();
+
+    build_manpages(&path)?;
+
+    Ok(())
+}