# HG changeset patch # User Raphaël Gomès # Date 1585127192 -3600 # Node ID c13cbc3872c8488695d29801d6dd2fb3c5c03436 # Parent d31d1c0685be1e58ef3d998221c11012ade3bb2c rust: update README to reflect use of `regex` crate Differential Revision: https://phab.mercurial-scm.org/D8325 diff -r d31d1c0685be -r c13cbc3872c8 rust/README.rst --- a/rust/README.rst Mon Mar 23 12:11:41 2020 +0100 +++ b/rust/README.rst Wed Mar 25 10:06:32 2020 +0100 @@ -36,15 +36,25 @@ One day we may use this environment variable to switch to new experimental 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 -all translated into regex. For compatibility and ease of development reasons -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 +all translated into regex. + +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 status code.