status: prefer relative paths in Rust code ? when the repository root is under the current directory, so the kernel needs to traverse fewer directory in every call to `read_dir` or `symlink_metadata`. Better yet would be to use libc functions like `openat` and `fstatat` to remove such repeated traversals entirely, but the standard library does not provide APIs based on those. Maybe with a crate like https://crates.io/crates/openat instead? Benchmarks of `rhg status` show that this patch is neutral in some configurations, and makes the command up to ~20% faster in others. Below is semi-arbitrary subset of results. The four numeric columns are: time (in seconds) with this changeset?s parent, time with this changeset, time difference (negative is better), time ratio (less than 1?is better). ``` mercurial-dirstate-v1 | default-plain-clean.no-iu.pbr | 0.0061 -> 0.0059: -0.0002 (0.97) mercurial-dirstate-v2 | default-plain-clean.no-iu.pbr | 0.0029 -> 0.0028: -0.0001 (0.97) mozilla-dirstate-v1 | default-plain-clean.no-iu.pbr | 0.2110 -> 0.2102: -0.0007 (1.00) mozilla-dirstate-v2 | default-copies-clean.ignored.pbr | 0.0489 -> 0.0401: -0.0088 (0.82) mozilla-dirstate-v2 | default-copies-clean.no-iu.pbr | 0.0479 -> 0.0393: -0.0085 (0.82) mozilla-dirstate-v2 | default-copies-large.all.pbr | 0.1262 -> 0.1210: -0.0051 (0.96) mozilla-dirstate-v2 | default-copies-small.ignored-unknown.pbr | 0.1262 -> 0.1200: -0.0062 (0.95) mozilla-dirstate-v2 | default-copies-small.ignored.pbr | 0.0536 -> 0.0417: -0.0119 (0.78) mozilla-dirstate-v2 | default-copies-small.no-iu.pbr | 0.0482 -> 0.0393: -0.0089 (0.81) mozilla-dirstate-v2 | default-plain-clean.ignored.pbr | 0.0518 -> 0.0402: -0.0116 (0.78) mozilla-dirstate-v2 | default-plain-clean.no-iu.pbr | 0.0481 -> 0.0392: -0.0088 (0.82) mozilla-dirstate-v2 | default-plain-large.all.pbr | 0.1271 -> 0.1218: -0.0052 (0.96) mozilla-dirstate-v2 | default-plain-small.ignored-unknown.pbr | 0.1225 -> 0.1202: -0.0022 (0.98) mozilla-dirstate-v2 | default-plain-small.ignored.pbr | 0.0510 -> 0.0418: -0.0092 (0.82) mozilla-dirstate-v2 | default-plain-small.no-iu.pbr | 0.0480 -> 0.0394: -0.0086 (0.82) netbeans-dirstate-v1 | default-plain-clean.no-iu.pbr | 0.1442 -> 0.1422: -0.0020 (0.99) netbeans-dirstate-v2 | default-plain-clean.no-iu.pbr | 0.0325 -> 0.0282: -0.0043 (0.87) ``` Differential Revision: https://phab.mercurial-scm.org/D12175

// testing.rs
//
// Copyright 2018 Georges Racinet <georges.racinet@octobus.net>
//
// 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::{Graph, GraphError, Revision, NULL_REVISION};

/// A stub `Graph`, same as the one from `test-ancestor.py`
///
/// o  13
/// |
/// | o  12
/// | |
/// | | o    11
/// | | |\
/// | | | | o  10
/// | | | | |
/// | o---+ |  9
/// | | | | |
/// o | | | |  8
///  / / / /
/// | | o |  7
/// | | | |
/// o---+ |  6
///  / / /
/// | | o  5
/// | |/
/// | o  4
/// | |
/// o |  3
/// | |
/// | o  2
/// |/
/// o  1
/// |
/// o  0
#[derive(Clone, Debug)]
pub struct SampleGraph;

impl Graph for SampleGraph {
    fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
        match rev {
            0 => Ok([NULL_REVISION, NULL_REVISION]),
            1 => Ok([0, NULL_REVISION]),
            2 => Ok([1, NULL_REVISION]),
            3 => Ok([1, NULL_REVISION]),
            4 => Ok([2, NULL_REVISION]),
            5 => Ok([4, NULL_REVISION]),
            6 => Ok([4, NULL_REVISION]),
            7 => Ok([4, NULL_REVISION]),
            8 => Ok([NULL_REVISION, NULL_REVISION]),
            9 => Ok([6, 7]),
            10 => Ok([5, NULL_REVISION]),
            11 => Ok([3, 7]),
            12 => Ok([9, NULL_REVISION]),
            13 => Ok([8, NULL_REVISION]),
            r => Err(GraphError::ParentOutOfRange(r)),
        }
    }
}

// A Graph represented by a vector whose indices are revisions
// and values are parents of the revisions
pub type VecGraph = Vec<[Revision; 2]>;

impl Graph for VecGraph {
    fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
        Ok(self[rev as usize])
    }
}