Remove baseline warning

[strega-nil]

we don't want people to use baseline necessarily; builtin-baseline is also completely valid.

[ras0219-msft]

We should warn if m_baseline_identifier.empty() && !baseline.empty()

[strega-nil]

hrm, okay.

[strega-nil]

I'm not sure about this; for example:

vcpkg.json:

{
  ...,
  "builtin-baseline": "b1"

vcpkg-configuration.json:

{
  "registries": [
    {
      "kind": "builtin",
      "baseline": "b2",
      "packages": [ "a", "b", "c" ]
    }
  ]
}

[ras0219-msft]

Right; so in this case we should warn to the user about which of the two baselines they've specified will be used (I assume b2?). I could see an argument for not warning iff they are the same.

[strega-nil]

I mean, they'll both be used: b2 will be used for packages a, b, and c, and b1 will be used for everything else.

[ras0219-msft]

What is the syntax for changing the default registry's baseline? I suspect this means we should warn in the case that the user has specified "builtin-baseline" AND specifies "default-registry". If that is already the case in this PR, then this comment is resolved.

[strega-nil]

The syntax for changing the default registry's baseline is:

{
  "default-registry": {
    "kind": "...",
    ...,
    "baseline": "<baseline>"
  }
}

This is not warned against in this PR; what should the warning look like, do you think?

[ras0219-msft]

"Warning: Specifying the "default-registry" overrides the "builtin-baseline" field. Pass to suppress this warning message."

[strega-nil]

Do we only want builtin-baseline to do something to a registry that is both builtin, and default? Currently it does something to registries that are builtin, even if they're non-default.

[ras0219-msft]

It should only affect the default builtin baseline in my opinion. I see the following scenarios:

1. No vcpkg-configuration.json (no warn)
2. adds other registries but doesn't change the default (no warn)
3. doesn't change the default, but does re-add the builtin registry to get packages with a different baseline (no warn)
4. re-defines the default to builtin, but at a different baseline (warn)

I think the most straightforward UX is all registries defined in the configuration file must have a baseline specified. Therefore, the only case that builtin-baseline could possibly apply would be in the undefined default case.