rust-dirstate: call parse/pack bindings from Python A future patch will need to address the issue of Rust module policy, to avoid having ugly duplicate imports and conditionals all over the place. As the rewrite of dirstate in Rust progresses, we will need fewer of those "contact points". Differential Revision: https://phab.mercurial-scm.org/D6350

rust-dirstate: add rust-cpython bindings to the new parse/pack functions This allows for Python code to call `parse/pack_dirstate` transparently. These bindings are heavy given the relatively simple task, as they are bound to implementation details of both the C and Python code. They will be slimmed down in future patches and eventually completely removed once more of the dirstate code has been refactored/rewritten in Rust. Both functions emulate the mutate-on-loop style of the Python and C implementations by looping over changed items in the compatibility layer, instead of at the core functions. Differential Revision: https://phab.mercurial-scm.org/D6349

rust-dirstate: add rust implementation of `parse_dirstate` and `pack_dirstate` Working towards the goal of having a complete Rust implementation of `hg status`, these two utils are a first step of many to be taken to improve performance and code maintainability. Two dependencies have been added: `memchr` and `byteorder`. Both of them have been written by reputable community members and are very mature crates. The Rust code will often need to use their byte-oriented functions. A few unit tests have been added and may help future development and debugging. In a future patch that uses `parse_dirstate` to stat the working tree in parallel - which neither the Python nor the C implementations do - actual performance improvements will be seen for larger repositories. Differential Revision: https://phab.mercurial-scm.org/D6348