Add xtask installing man pages

.cargo/config.toml

@@ -0,0 +1,2 @@
+[alias]
+xtask = "run --package xtask --"

Cargo.toml

@@ -5,7 +5,8 @@ members = [
     "pineappl_capi",
     "pineappl_cli",
     "pineappl_fastnlo",
-    "pineappl_py"
+    "pineappl_py",
+    "xtask",
 ]
 default-members = [
     "pineappl",

xtask/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "xtask"
+publish = false
+
+categories.workspace = true
+edition.workspace = true
+keywords.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+version.workspace = true
+
+[dependencies]
+anyhow = "1.0.68"
+clap = { features = ["string"], version = "4.2.0" }
+clap_mangen = "0.2.7"
+#git2 = "0.17.2"
+#semver = "1.0.17"
+pineappl_cli = { path = "../pineappl_cli", version = "0.6.1" }

xtask/src/main.rs

@@ -0,0 +1,55 @@
+use anyhow::Result;
+use std::env;
+use std::path::Path;
+
+fn main() -> Result<()> {
+    let args: Vec<_> = env::args().skip(1).collect();
+
+    match args.as_slice() {
+        [cmd, path] if cmd == "install-manpages" => install_manpages(Path::new(path)),
+        _ => todo!(),
+    }
+}
+
+fn install_manpages(path: &Path) -> Result<()> {
+    use clap::CommandFactory;
+    use clap_mangen::Man;
+    use std::fs::File;
+    use std::io::BufWriter;
+
+    fn render_manpages(path: &Path, cmd: &clap::Command) -> Result<()> {
+        let name = cmd
+            .get_bin_name()
+            .unwrap_or(cmd.get_name())
+            .replace(" ", "-");
+        let version = cmd
+            .get_version()
+            .map(|version| version.strip_prefix('v').unwrap().to_string());
+
+        // set the correct name of the command
+        let mut man_cmd = cmd.clone().name(name.clone());
+
+        // if there is a version, remove the 'v'
+        if let Some(version) = version {
+            man_cmd = man_cmd.version(version);
+        }
+
+        Man::new(man_cmd).render(&mut BufWriter::new(File::create(
+            path.join(format!("{name}.1")),
+        )?))?;
+
+        for subcmd in cmd.get_subcommands() {
+            render_manpages(path, subcmd)?;
+        }
+
+        Ok(())
+    }
+
+    let mut cmd = pineappl_cli::Opts::command();
+    // this is needed so subcommands return the correct `bin_name`
+    cmd.build();
+
+    render_manpages(path, &cmd)?;
+
+    Ok(())
+}