cargo-fmt-diff.rs

use git2::Delta;
use git2::DiffOptions;
use git2::Repository;
use std::collections::BTreeMap;
use std::env::set_current_dir;
use std::process::Command;

fn main() {
    let repo = Repository::open_from_env().unwrap();
    set_current_dir(repo.workdir().unwrap()).unwrap();

    let head = repo.head().unwrap().peel_to_tree().unwrap();

    let mut diff_options = DiffOptions::new();
    diff_options.include_untracked(true);
    diff_options.recurse_untracked_dirs(true);
    diff_options.show_untracked_content(true);
    diff_options.context_lines(0);
    let diff = repo
        .diff_tree_to_workdir(Some(&head), Some(&mut diff_options))
        .unwrap();

    let mut changed_files = BTreeMap::new();
    diff.foreach(
        &mut |_, _| true,
        Some(&mut |_, _| true),
        Some(&mut |delta, hunk| {
            if delta.new_file().path().unwrap().extension() != Some("rs".as_ref()) {
                return true;
            }
            match delta.status() {
                Delta::Unmodified
                | Delta::Deleted
                | Delta::Typechange
                | Delta::Unreadable
                | Delta::Conflicted => true,
                Delta::Added
                | Delta::Modified
                | Delta::Renamed
                | Delta::Copied
                | Delta::Untracked
                | Delta::Ignored => {
                    changed_files
                        .entry(delta.new_file().path().unwrap().to_path_buf())
                        .or_insert(vec![])
                        .push(hunk.new_start()..=hunk.new_start() + hunk.new_lines() - 1);
                    true
                }
            }
        }),
        None,
    )
    .unwrap();

    // Flatten into a `Vec` so we can use `.chunks(n)`.
    let changed_files: Vec<_> = changed_files.into_iter().collect();
    for changed_files in changed_files.chunks(100) {
        let mut changes_json = String::new();
        changes_json.push('[');
        for (path, ranges) in changed_files {
            let path = format!("{:?}", path.to_str().unwrap());
            for range in ranges {
                changes_json.push_str(&format!(
                    "{{\"file\":{},\"range\":[{},{}]}},",
                    path,
                    range.start(),
                    range.end(),
                ));
            }
        }
        changes_json.pop();
        changes_json.push(']');

        Command::new("rustfmt")
            .args(&[
                "--unstable-features",
                "--file-lines",
                &changes_json,
                "--skip-children",
                "--edition=2018",
            ])
            .args(changed_files.iter().map(|(path, _)| path))
            .status()
            .unwrap();
    }
}