rust/README.rst
author Martin von Zweigbergk <martinvonz@google.com>
Tue, 14 May 2019 16:30:38 -0700
changeset 42369 6310180662f5
parent 35569 964212780daf
child 44114 8a3b045d9086
permissions -rw-r--r--
commit: move sorting of added and removed files list to lower level localrepo.commitctx() has lists of all changed files, as well as lists of added and removed files. The list of all files is unsorted and changelog.add() will sort it. Let's also sort the lists of added and removed files at a lower level (manifestrevlog.add()) for consistency. It also seems safer to do it there, just before we write them to the store. That way other callers won't be able to create invalid commits (or whatever the consequence is) by passing in unsorted lists. Also, alternative storages may not care that the lists are sorted. I don't think this will be a performance problem (someone should have fixed the sorting in changelog.add() if it were). Differential Revision: https://phab.mercurial-scm.org/D6390

===================
Mercurial Rust Code
===================

This directory contains various Rust code for the Mercurial project.

The top-level ``Cargo.toml`` file defines a workspace containing
all primary Mercurial crates.

Building
========

To build the Rust components::

   $ cargo build

If you prefer a non-debug / release configuration::

   $ cargo build --release

Features
--------

The following Cargo features are available:

localdev (default)
   Produce files that work with an in-source-tree build.

   In this mode, the build finds and uses a ``python2.7`` binary from
   ``PATH``. The ``hg`` binary assumes it runs from ``rust/target/<target>hg``
   and it finds Mercurial files at ``dirname($0)/../../../``.

Build Mechanism
---------------

The produced ``hg`` binary is *bound* to a CPython installation. The
binary links against and loads a CPython library that is discovered
at build time (by a ``build.rs`` Cargo build script). The Python
standard library defined by this CPython installation is also used.

Finding the appropriate CPython installation to use is done by
the ``python27-sys`` crate's ``build.rs``. Its search order is::

1. ``PYTHON_SYS_EXECUTABLE`` environment variable.
2. ``python`` executable on ``PATH``
3. ``python2`` executable on ``PATH``
4. ``python2.7`` executable on ``PATH``

Additional verification of the found Python will be performed by our
``build.rs`` to ensure it meets Mercurial's requirements.

Details about the build-time configured Python are built into the
produced ``hg`` binary. This means that a built ``hg`` binary is only
suitable for a specific, well-defined role. These roles are controlled
by Cargo features (see above).

Running
=======

The ``hgcli`` crate produces an ``hg`` binary. You can run this binary
via ``cargo run``::

   $ cargo run --manifest-path hgcli/Cargo.toml

Or directly::

   $ target/debug/hg
   $ target/release/hg

You can also run the test harness with this binary::

   $ ./run-tests.py --with-hg ../rust/target/debug/hg

.. note::

   Integration with the test harness is still preliminary. Remember to
   ``cargo build`` after changes because the test harness doesn't yet
   automatically build Rust code.