scaffold the CLI, logging and turn research into TODOs

xtask/src/main.rs

@@ -0,0 +1,22 @@
+use clap::{Parser, Subcommand};
+
+mod manpage;
+
+#[derive(Parser)]
+struct Cli {
+    #[command(subcommand)]
+    pub command: Command,
+}
+
+#[derive(Subcommand)]
+enum Command {
+    Manpage(manpage::Cli),
+}
+
+fn main() -> anyhow::Result<()> {
+    let cli = Cli::parse();
+
+    match cli.command {
+        Command::Manpage(cli) => manpage::main(cli),
+    }
+}

xtask/src/manpage.rs

@@ -0,0 +1,25 @@
+use std::path::PathBuf;
+
+use clap::{CommandFactory as _, Parser};
+
+/// Render the manpage of git-identity from its clap definition
+#[derive(Parser)]
+pub struct Cli {
+    /// The file in which to write the newly generated manpage
+    ///
+    /// By default, this is "target/git-identity.1"
+    out_file: Option<PathBuf>,
+}
+
+pub fn main(cli: Cli) -> anyhow::Result<()> {
+    let man = clap_mangen::Man::new(git_identity::cli::Cli::command());
+    let mut buffer: Vec<u8> = Default::default();
+    man.render(&mut buffer)?;
+
+    std::fs::write(
+        cli.out_file.unwrap_or_else(|| "./target/git-identity.1".into()),
+        buffer,
+    )?;
+
+    Ok(())
+}