rust: replace most "operation" structs with functions The hg-core crate has a partially-formed concept of "operation", represented as structs with constructors and a `run` method. Each struct?s contructor takes different parameters, and each `run` has a different return type. Constructors typically don?t do much more than store parameters for `run` to access them. There was a comment about adding an `Operation` trait when the language supports expressing something so general, but it?s hard to imagine how operations with such different APIs could be used in a generic context. This commit starts removing the concept of "operation", since those are pretty much just functions. Differential Revision: https://phab.mercurial-scm.org/D9595

use crate::commands::Command;
use crate::error::CommandError;
use crate::ui::Ui;
use format_bytes::format_bytes;
use hg::operations::find_root;
use hg::utils::files::get_bytes_from_path;

pub const HELP_TEXT: &str = "
Print the root directory of the current repository.

Returns 0 on success.
";

pub struct RootCommand {}

impl RootCommand {
    pub fn new() -> Self {
        RootCommand {}
    }
}

impl Command for RootCommand {
    fn run(&self, ui: &Ui) -> Result<(), CommandError> {
        let path_buf = find_root()?;

        let bytes = get_bytes_from_path(path_buf);

        ui.write_stdout(&format_bytes!(b"{}\n", bytes.as_slice()))?;

        Ok(())
    }
}