girt 0.8.0

An incremental, idiomatic Rust implementation of Git
Documentation 
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//! Selection walks must not inherit their first-copy hash omission after packed damage.
use std::fs;

use super::*;
use crate::pack::counters;
use crate::pack_git::Fixture;

#[test]
fn selection_fallback_hashes_each_copy_and_clones_skip_damage() {
    let fixture = Fixture::new(ObjectFormat::Sha1, true, 4);
    let original = fs::read(&fixture.index_path).unwrap();
    let width = 20;
    let count = fixture.records.len();
    let names = &original[1032..1032 + count * width];
    let position = names
        .chunks_exact(width)
        .position(|name| name == fixture.ordinary.as_bytes())
        .unwrap();
    let other = (position + 1) % count;
    let crcs = 1032 + count * width;
    let offsets = crcs + count * 4;
    let first = fixture.repo.object_dir().join("pack/a.idx");
    let second = fixture.repo.object_dir().join("pack/z.idx");
    let pack = fs::read(fixture.index_path.with_extension("pack")).unwrap();
    fs::write(first.with_extension("pack"), &pack).unwrap();
    fs::write(second.with_extension("pack"), &pack).unwrap();
    let mut crc_damage = original.clone();
    crc_damage[crcs + position * 4] ^= 1;
    rehash(&mut crc_damage);
    fs::write(&first, crc_damage).unwrap();
    let mut identity_damage = original;
    for byte in 0..4 {
        identity_damage.swap(crcs + position * 4 + byte, crcs + other * 4 + byte);
        identity_damage.swap(offsets + position * 4 + byte, offsets + other * 4 + byte);
    }
    rehash(&mut identity_damage);
    fs::write(&second, identity_damage).unwrap();
    fs::remove_file(&fixture.index_path).unwrap();
    fs::remove_file(fixture.index_path.with_extension("pack")).unwrap();
    let objects = fixture.repo.objects(PackLimits::default()).unwrap();
    let clone = objects.clone();
    let cancel = AtomicBool::new(false);
    assert!(
        objects
            .read_unverified(fixture.ordinary, ReadLimits::default(), &cancel)
            .is_err()
    );
    counters::reset();
    assert!(clone.read(fixture.ordinary, ReadLimits::default()).is_err());
    assert_eq!(counters::OS_READS.with(|reads| reads.get()), 0);
    assert_eq!(
        objects
            .read(fixture.delta, ReadLimits::default())
            .unwrap()
            .unwrap()
            .id(),
        fixture.delta
    );
    assert!(fixture.root.path().exists());
}

fn rehash(bytes: &mut [u8]) {
    let end = bytes.len() - 20;
    let checksum = ObjectFormat::Sha1.checksum(&bytes[..end]);
    bytes[end..].copy_from_slice(checksum.as_bytes());
}

#[test]
fn independently_refreshed_clones_share_new_pack_damage() {
    let fixture = Fixture::new(ObjectFormat::Sha1, true, 4);
    let mut first = fixture.repo.objects(PackLimits::default()).unwrap();
    let mut second = first.clone();
    counters::reset();
    assert_eq!(
        first
            .read(fixture.ordinary, ReadLimits::default())
            .unwrap()
            .unwrap()
            .id(),
        fixture.ordinary
    );
    let healthy_reads = counters::OS_READS.with(|reads| reads.get());
    let new = fixture.repo.object_dir().join("pack/a-new.idx");
    fs::copy(
        fixture.index_path.with_extension("pack"),
        new.with_extension("pack"),
    )
    .unwrap();
    let mut bytes = fs::read(&fixture.index_path).unwrap();
    let position = bytes[1032..1032 + fixture.records.len() * 20]
        .as_chunks::<20>()
        .0
        .iter()
        .position(|name| name == fixture.ordinary.as_bytes())
        .unwrap();
    bytes[1032 + fixture.records.len() * 20 + position * 4] ^= 1;
    rehash(&mut bytes);
    fs::write(new, bytes).unwrap();
    first
        .refresh(PackLimits::default(), AlternateLimits::default())
        .unwrap();
    second
        .refresh(PackLimits::default(), AlternateLimits::default())
        .unwrap();
    assert_eq!(
        first
            .read(fixture.ordinary, ReadLimits::default())
            .unwrap()
            .unwrap()
            .id(),
        fixture.ordinary
    );
    counters::reset();
    assert_eq!(
        second
            .read(fixture.ordinary, ReadLimits::default())
            .unwrap()
            .unwrap()
            .id(),
        fixture.ordinary
    );
    assert_eq!(counters::OS_READS.with(|reads| reads.get()), healthy_reads);
}