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Differential D8325

rust: update README to reflect use of `regex` crate
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Authored by Alphare on Mar 25 2020, 5:38 AM.

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rHGc13cbc3872c8: rust: update README to reflect use of `regex` crate

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Alphare created this revision.Mar 25 2020, 5:38 AM
Alphare added a commit: rHGc13cbc3872c8: rust: update README to reflect use of `regex` crate.Mar 25 2020, 4:32 PM
This revision was not accepted when it landed; it landed in state Needs Review.
Closed by commit rHGc13cbc3872c8: rust: update README to reflect use of `regex` crate (authored by Alphare). · Explain Why
This revision was automatically updated to reflect the committed changes.

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Mrust/README.rst (22 lines)

Diff 20882

rust/README.rst

If the environment variable ``HGWITHRUSTEXT=cpython`` is set, the Rust If the environment variable ``HGWITHRUSTEXT=cpython`` is set, the Rust
extension will be used by default unless ``--no-rust``. extension will be used by default unless ``--no-rust``.
One day we may use this environment variable to switch to new experimental One day we may use this environment variable to switch to new experimental
binding crates like a hypothetical ``HGWITHRUSTEXT=hpy``. binding crates like a hypothetical ``HGWITHRUSTEXT=hpy``.
Using the full ``hg status`` extension Using the fastest ``hg status``
-------------------------------------- -------------------------------
The code for ``hg status`` needs to conform to ``.hgignore`` rules, which are The code for ``hg status`` needs to conform to ``.hgignore`` rules, which are
all translated into regex. For compatibility and ease of development reasons all translated into regex.
the Re2 regex engine is in use until we figure out if the ``regex`` crate has
similar enough behavior. This implies that you need to install ``Re2``
following Google's guidelines: https://github.com/google/re2/wiki/Install
In the first version, for compatibility and ease of development reasons, the
Re2 regex engine was chosen until we figured out if the ``regex`` crate had
similar enough behavior.
Now that that work has been done, the default behavior is to use the ``regex``
crate, that provides a significant performance boost compared to the standard
Python + C path in many commands such as ``status``, ``diff`` and ``commit``,
However, the ``Re2`` path remains slightly faster for our use cases and remains
a better option for getting the most speed out of your Mercurial.
If you want to use ``Re2``, you need to install ``Re2`` following Google's
guidelines: https://github.com/google/re2/wiki/Install
Then, use ``HG_RUST_FEATURES=with-re2`` when building ``hg`` to use the full Then, use ``HG_RUST_FEATURES=with-re2`` when building ``hg`` to use the full
status code. status code.
Developing Rust Developing Rust
=============== ===============
The current version of Rust in use is ``1.34.2``, because it's what Debian The current version of Rust in use is ``1.34.2``, because it's what Debian
stable has. You can use ``rustup override set 1.34.2`` at the root of the repo stable has. You can use ``rustup override set 1.34.2`` at the root of the repo