wireproto: don't expose changegroupsubset capability if not available
We just marked the changegroupsubset command as only available to
version 1 of the wire transports. There is a capability of the same
name of the command that indicates if the command is supported.
This commit teaches the capabilities code to conditionally emit that
capability depending on whether the command is available for the
current transport.
Most test output is reordering of capabilities. But the limited tests
for version 2 of the SSH protocol do show the capability disappearing.
Differential Revision: https://phab.mercurial-scm.org/D2486
===================
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.