Feature/manpage (#596)

This PR adds a build script to generate a man page using clap_mangen, as
per this example:
https://github.com/sondr3/clap-man-example/blob/main/build.rs

I'm not sure what to actually do with the man file from here, I guess
it's up to the packaging process to do something with it?
See
#69 (comment)

Note I couldn't see a way to include the `DISPLAY` chunk names from the
constant as we did before. They're now just hardcoded into the help and
will require manually updating if the list changes.

Closes #526

---------

Co-authored-by: Alejandro González <[email protected]>

Author: andrews05

.gitignore

@@ -4,3 +4,4 @@ target
 *.out.png
 /.idea
 /node_modules
+/generated

Cargo.lock

@@ -78,6 +78,8 @@ features = ["png"]
 version = "0.24.6"
 
 [build-dependencies]
+clap = "4.3.8"
+clap_mangen = "0.2.12"
 rustc_version = "0.4.0"
 
 [features]
@@ -98,3 +100,11 @@ opt-level = 2
 lto = "fat"
 strip = "symbols"
 panic = "abort"
+
+[package.metadata.deb]
+assets = [
+    ["target/release/oxipng", "usr/bin/", "755"],
+    ["generated/assets/oxipng.1", "usr/share/man/man1/", "644"],
+    ["README.md", "usr/share/doc/oxipng/", "644"],
+    ["CHANGELOG.md", "usr/share/doc/oxipng/", "644"],
+]

Cargo.toml

@@ -0,0 +1,34 @@
+use std::{
+    env,
+    fs::File,
+    io::{BufWriter, Error},
+    path::Path,
+};
+
+use clap_mangen::Man;
+
+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 = BufWriter::new(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=src/display_chunks.rs");
+
+    // Create `generated/assets/` folder.
+    let path = env::current_dir()?.join("generated").join("assets");
+    std::fs::create_dir_all(&path).unwrap();
+
+    build_manpages(&path)?;
+
+    Ok(())
+}