# Oxidized Mercurial

This project provides a Rust implementation of the Mercurial (`hg`)

version control tool.

Under the hood, the project uses

[PyOxidizer](https://github.com/indygreg/PyOxidizer) to embed a Python

interpreter in a binary built with Rust. At run-time, the Rust `fn main()`

is called and Rust code handles initial process startup. An in-process

Python interpreter is started (if needed) to provide additional

functionality.

# Building

This project currently requires an unreleased version of PyOxidizer

(0.7.0-pre). For best results, build the exact PyOxidizer commit

as defined in the `pyoxidizer.bzl` file:

    $ git clone https://github.com/indygreg/PyOxidizer.git

    $ cd PyOxidizer

    $ git checkout <Git commit from pyoxidizer.bzl>

    $ cargo build --release

Then build this Rust project using the built `pyoxidizer` executable::

    $ /path/to/pyoxidizer/target/release/pyoxidizer build

If all goes according to plan, there should be an assembled application

under `build/<arch>/debug/app/` with an `hg` executable:

    $ build/x86_64-unknown-linux-gnu/debug/app/hg version

    Mercurial Distributed SCM (version 5.3.1+433-f99cd77d53dc+20200331)

    (see https://mercurial-scm.org for more information)

    This is free software; see the source for copying conditions. There is NO

    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

# Running Tests

To run tests with a built `hg` executable, you can use the `--with-hg`

argument to `run-tests.py`. But there's a wrinkle: many tests run custom

Python scripts that need to `import` modules provided by Mercurial. Since

these modules are embedded in the produced `hg` executable, a regular

Python interpreter can't access them! To work around this, set `PYTHONPATH`

to the Mercurial source directory. e.g.:

    $ cd /path/to/hg/src/tests

    $ PYTHONPATH=`pwd`/.. python3.7 run-tests.py \

        --with-hg `pwd`/../rust/hgcli/build/x86_64-unknown-linux-gnu/debug/app/hg