Mercurial Rust Code
This directory contains various Rust code for the Mercurial project. Rust is not required to use (or build) Mercurial, but using it improves performance in some areas.
There are currently three independent rust projects: - chg. An implementation of chg, in rust instead of C. - hgcli. A experiment for starting hg in rust rather than in python,
by linking with the python runtime. Probably meant to be replaced by PyOxidizer at some point.
- hg-core (and hg-cpython/hg-directffi): implementation of some functionality of mercurial in rust, e.g. ancestry computations in revision graphs or pull discovery. The top-level Cargo.toml file defines a workspace containing these crates.
Using hg-core
Local use (you need to clean previous build artifacts if you have built without rust previously):
$ HGWITHRUSTEXT=cpython make local # to use ./hg $ HGWITHRUSTEXT=cpython make tests # to run all tests $ (cd tests; HGWITHRUSTEXT=cpython ./run-tests.py) # only the .t $ ./hg debuginstall | grep rust # to validate rust is in use checking module policy (rust+c-allow)
Setting HGWITHRUSTEXT to other values like true is deprecated and enables only a fraction of the rust code.
Developing hg-core
Simply run:
$ cargo build --release
It is possible to build without --release, but it is not recommended if performance is of any interest: there can be an order of magnitude of degradation when removing --release.
For faster builds, you may want to skip code generation:
$ cargo check
You can run only the rust-specific tests (as opposed to tests of mercurial as a whole) with:
$ cargo test --all