contrib/win32/hg.bat

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

@echo off
rem Windows Driver script for Mercurial

setlocal
set HG=%~f0

rem Use a full path to Python (relative to this script) if it exists,
rem as the standard Python install does not put python.exe on the PATH...
rem Otherwise, expect that python.exe can be found on the PATH.
rem %~dp0 is the directory of this script

if exist "%~dp0..\python.exe" (
    "%~dp0..\python" "%~dp0hg" %*
) else (
    python "%~dp0hg" %*
)
endlocal

exit /b %ERRORLEVEL%