feat(versions): add support for $pkg keyword

[wmertens]

Description

When you use $pkg as the version in pnpm overrides, which should just use the version specified in dependencies, syncpack is unhappy.

Suggested Solution

replace $pkg by the package's version when comparing versions.

Help Needed

no idea where to start

[ricokahler]

Experiencing the same issue

Using "syncpack": "^12.3.3"

From the pnpm docs:

An override may be defined as a reference to a direct dependency's spec. This is achieved by prefixing the name of the dependency with a $:

{
  "dependencies": {
    "foo": "^1.0.0"
  },
  "pnpm": {
    "overrides": {
      "foo": "$foo"
    }
  }
}

Note that NPM overrides also supports this:

You may not set an override for a package that you directly depend on unless both the dependency and the override itself share the exact same spec. To make this limitation easier to deal with, overrides may also be defined as a reference to a spec for a direct dependency by prefixing the name of the package you wish the version to match with a $.

{
  "dependencies": {
    "foo": "^1.0.0"
  },
  "overrides": {
    // BAD, will throw an EOVERRIDE error
    // "foo": "^2.0.0"
    // GOOD, specs match so override is allowed
    // "foo": "^1.0.0"
    // BEST, the override is defined as a reference to the dependency
    "foo": "$foo",
    // the referenced package does not need to match the overridden one
    "bar": "$foo"
  }
}