refactor(man): rename EXTRA section to EXAMPLES and extract render function

Move man page rendering into a shared `src/man_page.rs` module (gated on
`cli-man` feature) so both the binary and sync test use the same logic.
Replace the `.SH EXTRA` section header with `.SH EXAMPLES` in the
generated output.

https://claude.ai/code/session_01CrXuWDMVQsiUBoy6ceACsF

Author: claude

Cargo.toml

@@ -92,7 +92,6 @@ zero-copy-pads = "0.2.0"
 
 [dev-dependencies]
 build-fs-tree = "0.8.1"
-clap_mangen = "0.2.27"
 command-extra = "1.0.0"
 libc = "0.2.182"
 maplit = "1.0.2"

cli/man_page.rs

@@ -1,13 +1,12 @@
-use clap::CommandFactory;
-use clap_mangen::Man;
-use parallel_disk_usage::args::Args;
-use std::{io::stdout, process::ExitCode};
+use parallel_disk_usage::man_page::render_man_page;
+use std::process::ExitCode;
 
 fn main() -> ExitCode {
-    let command = Args::command();
-    let man = Man::new(command);
-    match man.render(&mut stdout()) {
-        Ok(()) => ExitCode::SUCCESS,
+    match render_man_page() {
+        Ok(content) => {
+            print!("{content}");
+            ExitCode::SUCCESS
+        }
         Err(error) => {
             eprintln!("error: {error}");
             ExitCode::FAILURE

exports/pdu.1

@@ -98,7 +98,7 @@ Print version
 .TP
 [\fIFILES\fR]
 List of files and/or directories
-.SH EXTRA
+.SH EXAMPLES
 Examples:
     Show disk usage chart of current working directory
     $ pdu

src/lib.rs

@@ -14,6 +14,8 @@ pub use serde_json;
 pub mod app;
 #[cfg(feature = "cli")]
 pub mod args;
+#[cfg(feature = "cli-man")]
+pub mod man_page;
 #[cfg(feature = "cli")]
 pub mod runtime_error;
 #[cfg(feature = "cli")]

src/man_page.rs

@@ -0,0 +1,15 @@
+use crate::args::Args;
+use clap::CommandFactory;
+use clap_mangen::Man;
+use std::io;
+
+/// Renders the man page for `pdu` as a string.
+pub fn render_man_page() -> io::Result<String> {
+    let command = Args::command();
+    let man = Man::new(command);
+    let mut buffer = Vec::new();
+    man.render(&mut buffer)?;
+    let content = String::from_utf8(buffer)
+        .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+    Ok(content.replace("\n.SH EXTRA\n", "\n.SH EXAMPLES\n"))
+}

tests/sync_man_page.rs

@@ -5,19 +5,13 @@
 // Since the CLI in Windows looks a little different, and I am way too lazy to make two versions
 // of man page files, the following test would only run in UNIX-like environment.
 #![cfg(unix)]
-#![cfg(feature = "cli")]
+#![cfg(feature = "cli-man")]
 
-use clap::CommandFactory;
-use clap_mangen::Man;
-use parallel_disk_usage::args::Args;
+use parallel_disk_usage::man_page::render_man_page;
 
 #[test]
 fn man_page() {
-    let command = Args::command();
-    let man = Man::new(command);
-    let mut buffer = Vec::new();
-    man.render(&mut buffer).expect("render man page to buffer");
-    let received = String::from_utf8(buffer).expect("man page should be valid UTF-8");
+    let received = render_man_page().expect("render man page");
     let expected = include_str!("../exports/pdu.1");
     assert!(
         received == expected,