[vcpkg] Registries MVP

[strega-nil]

This adds everything except for git registries, which will be implemented later.

Note: this is a large change. You may want to look at each commit in turn.

See https://github.com/strega-nil/vcpkg-example/tree/trunk for an example of using registries :) (ignore the actual C++, that's not really what's important... no guarantees on it compiling, for example)

[edhebi]

In your example project, you specify both your local registry and the builtin one, with no default. Is it possible to only define a registry for some packages, and keep the builtin as a fallback ?

something like this:

{
  "name": "fmt-example",
  "version-string": "0.0.1",
  "dependencies": [
    "fmt",
     "zlib"
  ],
  "configuration": {
    "registries": [
      {
        "kind": "directory",
        "path": "my-registry",
        "packages": [ "zlib" ]
      }
    ]
  }
}

where the builtin registry is used automatically for fmt ?

[strega-nil]

@edhebi yep! The default registry defaults to the builtin one :) I'd definitely recommend reading the manifest RFC at #12881 for more info, and if you still have questions post them there :)

[BillyONeal]

No serious issues left other than Bill not being a fan of that one lambda. I don't agree with the "configuration" mechanism in the spec, but this does seem to implement what's in that spec.

[strega-nil]

@BillyONeal could you merge this today?

[BillyONeal]

Yes, but I thought we wanted another reviewer?

[ras0219]

Please also confirm everything still compiles using v140 and gcc-7:

FROM ubuntu:18.04

RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y \
  xz-utils \
  build-essential \
  tar \
  unzip \
  ninja-build \
  cmake \
  curl \
  vim \
  git \
  nasm \
  yasm \
  python3 \
  pkg-config \
  zip

CMD [ "/bin/bash" ]

docker run -it --rm 51d7a08f83a8 /bin/bash -c "git clone https://github.com/microsoft/vcpkg --depth=1 && vcpkg/bootstrap-vcpkg.sh"

// CMakeSettings.json
[
    {
      "name": "x64-Release-v140",
      "generator": "Visual Studio 16 2019 Win64",
      "configurationType": "RelWithDebInfo",
      "buildRoot": "${projectDir}\\out\\build\\${name}",
      "installRoot": "${projectDir}\\out\\install\\${name}",
      "cmakeCommandArgs": "-T v140 -DVCPKG_STANDARD_LIBRARY=msvc-stl -DVCPKG_WARNINGS_AS_ERRORS=OFF -DBUILD_TESTING=OFF",
      "buildCommandArgs": "/m",
      "ctestCommandArgs": "",
      "inheritEnvironments": [ "msvc_x64_x64" ],
      "variables": [],
      "environments": [ { "CL": "/MP" } ]
    }
]

[strega-nil]

@ras0219 fwiw, we compile with g++-7 in CI.

Also, I'll have a patch out later today to fix compilation with g++-6.

[BillyONeal]

Thanks for your contribution!