rust/hg-core/src/operations/cat.rs

ci: shard the test run on mac os X

This should comes with some benefit:
- spread the load across more runner,
- reduce the real-time CI run,
- reduce the "retry" run when we need them.

We start with the Mac jobs, but that would be tremendously useful for Windows
too.

For linux, we need to reduce the startup overhead for this to be worth it.
Building smaller image and speeding up clone should help with that.

// list_tracked_files.rs
//
// Copyright 2020 Antoine Cezar <[e-mail]>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

use crate::repo::Repo;
use crate::revlog::Node;
use crate::revlog::RevlogError;

use crate::utils::hg_path::HgPath;

use crate::errors::HgError;
use crate::manifest::Manifest;
use crate::manifest::ManifestEntry;
use itertools::put_back;
use itertools::PutBack;
use std::cmp::Ordering;

pub struct CatOutput<'a> {
    /// Whether any file in the manifest matched the paths given as CLI
    /// arguments
    pub found_any: bool,
    /// The contents of matching files, in manifest order
    pub results: Vec<(&'a HgPath, Vec<u8>)>,
    /// Which of the CLI arguments did not match any manifest file
    pub missing: Vec<&'a HgPath>,
    /// The node ID that the given revset was resolved to
    pub node: Node,
}

// Find an item in an iterator over a sorted collection.
fn find_item<'a>(
    i: &mut PutBack<impl Iterator<Item = Result<ManifestEntry<'a>, HgError>>>,
    needle: &HgPath,
) -> Result<Option<Node>, HgError> {
    loop {
        match i.next() {
            None => return Ok(None),
            Some(result) => {
                let entry = result?;
                match needle.as_bytes().cmp(entry.path.as_bytes()) {
                    Ordering::Less => {
                        i.put_back(Ok(entry));
                        return Ok(None);
                    }
                    Ordering::Greater => continue,
                    Ordering::Equal => return Ok(Some(entry.node_id()?)),
                }
            }
        }
    }
}

// Tuple of (missing, found) paths in the manifest
type ManifestQueryResponse<'a> = (Vec<(&'a HgPath, Node)>, Vec<&'a HgPath>);

fn find_files_in_manifest<'query>(
    manifest: &Manifest,
    query: impl Iterator<Item = &'query HgPath>,
) -> Result<ManifestQueryResponse<'query>, HgError> {
    let mut manifest = put_back(manifest.iter());
    let mut res = vec![];
    let mut missing = vec![];

    for file in query {
        match find_item(&mut manifest, file)? {
            None => missing.push(file),
            Some(item) => res.push((file, item)),
        }
    }
    Ok((res, missing))
}

/// Output the given revision of files
///
/// * `root`: Repository root
/// * `rev`: The revision to cat the files from.
/// * `files`: The files to output.
pub fn cat<'a>(
    repo: &Repo,
    revset: &str,
    mut files: Vec<&'a HgPath>,
) -> Result<CatOutput<'a>, RevlogError> {
    let rev = crate::revset::resolve_single(revset, repo)?;
    let manifest = repo.manifest_for_rev(rev.into())?;
    let node = *repo
        .changelog()?
        .node_from_rev(rev.into())
        .expect("should succeed when repo.manifest did");
    let mut results: Vec<(&'a HgPath, Vec<u8>)> = vec![];
    let mut found_any = false;

    files.sort_unstable();

    let (found, missing) =
        find_files_in_manifest(&manifest, files.into_iter())?;

    for (file_path, file_node) in found {
        found_any = true;
        let file_log = repo.filelog(file_path)?;
        results.push((
            file_path,
            file_log.data_for_node(file_node)?.into_file_data()?,
        ));
    }

    Ok(CatOutput {
        found_any,
        results,
        missing,
        node,
    })
}