rust/hg-core/src/dirstate/mod.rs

rust-dirstate: add "dirs" Rust implementation

Following the work done in d1786c1d34fa and working towards the goal of a
complete Rust implementation of the dirstate, this rewrites the `dirs` class.

There is already a C implementation, which relies heavily on CPython hacks and
protocol violations for performance, so I don't expect this to perform as well
for now, as this is very straight-forward code.
The immediate benefits are new high-level documentation and some unit tests.

Differential Revision: https://phab.mercurial-scm.org/D6393

pub mod dirs_multiset;
pub mod parsers;

#[derive(Debug, PartialEq, Copy, Clone)]
pub struct DirstateParents<'a> {
    pub p1: &'a [u8],
    pub p2: &'a [u8],
}

/// The C implementation uses all signed types. This will be an issue
/// either when 4GB+ source files are commonplace or in 2038, whichever
/// comes first.
#[derive(Debug, PartialEq)]
pub struct DirstateEntry {
    pub state: i8,
    pub mode: i32,
    pub mtime: i32,
    pub size: i32,
}

pub type DirstateVec = Vec<(Vec<u8>, DirstateEntry)>;

#[derive(Debug, PartialEq)]
pub struct CopyVecEntry<'a> {
    pub path: &'a [u8],
    pub copy_path: &'a [u8],
}

pub type CopyVec<'a> = Vec<CopyVecEntry<'a>>;

/// The Python implementation passes either a mapping (dirstate) or a flat
/// iterable (manifest)
pub enum DirsIterable {
    Dirstate(DirstateVec),
    Manifest(Vec<Vec<u8>>),
}