Crate hg_parser

hg-parser

Mercurial repository parser written in the Rust programming language.

Basic usage

Add dependency to Cargo.toml

[dependencies]
hg-parser = "0.9"

Use case - Analyse revision log and export to git fast-import format

use std::{
    env::args,
    io::Write,
    path::{Path, PathBuf},
    string::ParseError,
    time::Instant,
};

use hg_parser::{file_content, FileType, ManifestEntryDetails, MercurialRepository, Revision};

fn main() -> Result<(), Error> {
    let path: PathBuf = args().nth(1).expect("path not provided").parse()?;
    export_repo(path)
}

fn export_repo<P: AsRef<Path>>(path: P) -> Result<(), Error> {
    let start = Instant::now();
    let repo = MercurialRepository::open(path)?;

    let stdout = std::io::stdout();
    let mut writer = stdout.lock();

    for changeset in &repo {
        let revision = changeset.revision;
        eprintln!("rev: {:?}", revision);

        let header = &changeset.header;
        let mut branch = None;
        let mut closed = false;
        for (key, value) in &header.extra {
            if key == b"branch" {
                branch = Some(value.as_slice());
            }

            if key == b"close" && value == b"1" {
                closed = true;
            }
        }

        let mut branch: Vec<_> = branch.unwrap_or(b"master").into();
        for b in branch.iter_mut() {
            if *b == b' ' {
                *b = b'-';
            }
        }

        let user = String::from_utf8_lossy(&header.user);
        let desc = String::from_utf8_lossy(&header.comment);

        let time = header.time.timestamp_secs();
        let timezone = header.time.tz_offset_secs();
        let tz = format!("{:+03}{:02}", -timezone / 3600, ((-timezone % 3600) / 60));

        write!(writer, "reset refs/heads/")?;
        writer.write_all(&branch)?;
        write!(writer, "\ncommit refs/heads/")?;
        writer.write_all(&branch)?;
        writeln!(writer, "\nmark :{}", mark(revision))?;

        writeln!(writer, "author {} {} {}", user, time, tz)?;
        writeln!(writer, "committer {} {} {}", user, time, tz)?;
        writeln!(writer, "data {}", desc.len() + 1)?;
        writeln!(writer, "{}\n", desc)?;

        match (header.p1, header.p2) {
            (Some(p1), Some(p2)) => {
                writeln!(writer, "from :{}", mark(p1))?;
                writeln!(writer, "merge :{}", mark(p2))?;
            }
            (Some(p), None) | (None, Some(p)) => {
                writeln!(writer, "from :{}", mark(p))?;
            }
            _ => (),
        }

        for file in changeset.files {
            match (file.data, file.manifest_entry) {
                (None, None) => {
                    write!(writer, "D ")?;
                    writer.write_all(&file.path)?;
                    writeln!(writer)?;
                }
                (Some(data), Some(manifest_entry)) => {
                    write!(
                        writer,
                        "M {} inline ",
                        match manifest_entry.details {
                            ManifestEntryDetails::File(FileType::Symlink) => "120000",
                            ManifestEntryDetails::File(FileType::Executable) => "100755",
                            ManifestEntryDetails::Tree
                            | ManifestEntryDetails::File(FileType::Regular) => "100644",
                        }
                    )?;
                    writer.write_all(&file.path)?;
                    let data = file_content(&data);
                    writeln!(writer, "\ndata {}", data.len())?;
                    writer.write_all(data)?;
                }
                _ => panic!("Wrong file data!"),
            }
        }

        if closed {
            write!(writer, "reset refs/tags/archive/")?;
            writer.write_all(&branch)?;
            writeln!(writer, "\nfrom :{}\n", mark(revision))?;

            write!(writer, "reset refs/heads/")?;
            writer.write_all(&branch)?;
            writeln!(writer, "\nfrom 0000000000000000000000000000000000000000\n")?;
        }
    }

    for (rev, tag) in repo.tags().unwrap() {
        eprintln!("export tag {}", tag.name);
        writeln!(writer, "reset refs/tags/{}", tag.name).unwrap();
        writeln!(writer, "from :{}", mark(rev)).unwrap();
        writeln!(writer).unwrap();
    }

    eprintln!("Done. Elapsed: {:?}", start.elapsed());
    Ok(())
}

fn mark<R: Into<Revision>>(rev: R) -> usize {
    (rev.into() + 1).0 as usize
}

#[derive(Debug)]
#[allow(dead_code)]
enum Error {
    MercurialRepoException(hg_parser::ErrorKind),
    Parse(ParseError),
    IO(std::io::Error),
}

impl From<ParseError> for Error {
    fn from(value: ParseError) -> Self {
        Error::Parse(value)
    }
}

impl From<std::io::Error> for Error {
    fn from(value: std::io::Error) -> Self {
        Error::IO(value)
    }
}

impl From<hg_parser::ErrorKind> for Error {
    fn from(value: hg_parser::ErrorKind) -> Self {
        Error::MercurialRepoException(value)
    }
}

Implementation details

hg-parser is based on repository parse code from mononoke project. Which basically based on original Mercurial source code. Version has some simplifications which may not work for you.

Structs

CachedMercurialRepository

Cached version of MercurialRepository.

Changeset

Changeset info about revision, contains revision number, header and files with bodies and metadata.

ChangesetFile

Changeset’s file. Contains path info, internal blob from Mercurial (use file_content for actual file data) and meta information.

ChangesetHeader

Changeset’s header.

ChangesetHeaderIter

ChangesetIter

Iterator over MercurialRepository revisions.

ManifestEntry

Manifest entry for file. Contains revision hash and file metainformation.

MercurialRepository

Mercurial repository. Top-level structure for access to change sets and tags.

MercurialRepositoryOptions

Options for mercurial repository.

Revision

Mercurial revision’s index.

RevisionRange

An iterator over a range of Revision.

SharedMercurialRepository

Shares instance of CachedMercurialRepository between multiple readers.

Enums

ErrorKind

FileType

File type. Can be regular, executable, or symlink.

ManifestEntryDetails

File meta information.

Functions

file_content

Extract blob data (raw file content) from internal Mercurial representation. This representation is by default returned by ChangesetIter iterator.