summary.rs

#[macro_use]
extern crate failure_derive;

...


#[derive(Debug, Fail)]
enum RuntimeError {
    CannotFindRoot { cwd: PathBuf },
}

impl fmt::Display for RuntimeError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            RuntimeError::CannotFindRoot { cwd: cwd } => write!(
                f,
                "Could not find a VCS checkout root starting from {}",
                cwd.to_string_lossy()
            ),
        }
    }
}

...

    fn set_root(&mut self) -> Result<(), Error> {
        let cwd = env::current_dir()?;
        let mut root = PathBuf::new();
        for anc in cwd.ancestors() {
            if self.is_checkout_root(&anc) {
                root.push(anc);
                self.root = Some(root);
                return Ok(());
            }
        }

        Err(RuntimeError::CannotFindRoot { cwd: cwd })
    }