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discovery: using the new basesheads()...
discovery: using the new basesheads() Our ultimate goal is to switch eventually to a Rust implementation, but this move actually seems to increase the performance in a pure Python build. What follows is a quick measurement done on PyPy on repos prepared with `contrib/discovery-helper.sh 50 100`. Before: ! wall 0.894384 comb 0.890000 user 0.890000 sys 0.000000 (best of 11) ! wall 0.971199 comb 0.970000 user 0.950000 sys 0.020000 (max of 11) ! wall 0.927993 comb 0.925455 user 0.919091 sys 0.006364 (avg of 11) ! wall 0.921619 comb 0.920000 user 0.910000 sys 0.010000 (median of 11) After: ! wall 0.614278 comb 0.610000 user 0.610000 sys 0.000000 (best of 14) ! wall 0.789459 comb 0.790000 user 0.770000 sys 0.020000 (max of 14) ! wall 0.722765 comb 0.720000 user 0.715714 sys 0.004286 (avg of 14) ! wall 0.734448 comb 0.720000 user 0.720000 sys 0.000000 (median of 14) Differential Revision: https://phab.mercurial-scm.org/D5583
Georges Racinet -
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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.