mergestate: split out merge state handling code from main merge module
There's already some pretty reasonable encapsulation here, but I want
to make the mergestate storage a property of the context so memctx
instances can do a reasonable thing. This is the first step in a
reshuffle to make that easier.
Differential Revision: https://phab.mercurial-scm.org/D8550
// Copyright 2018-2020 Georges Racinet <georges.racinet@octobus.net>
// and Mercurial contributors
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.
//! Mercurial concepts for handling revision history
pub mod node;
pub mod nodemap;
pub use node::{Node, NodeError, NodePrefix, NodePrefixRef};
/// Mercurial revision numbers
///
/// As noted in revlog.c, revision numbers are actually encoded in
/// 4 bytes, and are liberally converted to ints, whence the i32
pub type Revision = i32;
/// Marker expressing the absence of a parent
///
/// Independently of the actual representation, `NULL_REVISION` is guaranteed
/// to be smaller than all existing revisions.
pub const NULL_REVISION: Revision = -1;
/// Same as `mercurial.node.wdirrev`
///
/// This is also equal to `i32::max_value()`, but it's better to spell
/// it out explicitely, same as in `mercurial.node`
pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff;
/// The simplest expression of what we need of Mercurial DAGs.
pub trait Graph {
/// Return the two parents of the given `Revision`.
///
/// Each of the parents can be independently `NULL_REVISION`
fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError>;
}
#[derive(Clone, Debug, PartialEq)]
pub enum GraphError {
ParentOutOfRange(Revision),
WorkingDirectoryUnsupported,
}
/// The Mercurial Revlog Index
///
/// This is currently limited to the minimal interface that is needed for
/// the [`nodemap`](nodemap/index.html) module
pub trait RevlogIndex {
/// Total number of Revisions referenced in this index
fn len(&self) -> usize;
/// Return a reference to the Node or `None` if rev is out of bounds
///
/// `NULL_REVISION` is not considered to be out of bounds.
fn node(&self, rev: Revision) -> Option<&Node>;
}