rust-node: binary Node ID and conversion utilities The choice of type makes sure that a `Node` has the exact wanted size. We'll use a different type for prefixes. Added dependency: hexadecimal conversion relies on the `hex` crate. The fact that sooner or later Mercurial is going to need to change its hash sizes has been taken strongly in consideration: - the hash length is a constant, but that is not directly exposed to callers. Changing the value of that constant is the only thing to do to change the hash length (even in unit tests) - the code could be adapted to support several sizes of hashes, if that turned out to be useful. To that effect, only the size of a given `Node` is exposed in the public API. - callers not involved in initial computation, I/O and FFI are able to operate without a priori assumptions on the hash size. The traits `FromHex` and `ToHex` have not been directly implemented, so that the doc-comments explaining these restrictions would stay really visible in `cargo doc` Differential Revision: https://phab.mercurial-scm.org/D7788

[package]
name = "hg-core"
version = "0.1.0"
authors = ["Georges Racinet <gracinet@anybox.fr>"]
description = "Mercurial pure Rust core library, with no assumption on Python bindings (FFI)"
edition = "2018"

[lib]
name = "hg"

[dependencies]
byteorder = "1.3.1"
hex = "0.4.0"
lazy_static = "1.3.0"
memchr = "2.2.0"
rand = "0.6.5"
rand_pcg = "0.1.1"
rayon = "1.2.0"
regex = "1.1.0"
twox-hash = "1.5.0"