git dependencies are reported as outdated

[jens-duttke]

I have a dependency which is loaded from Github, since the projects version on npm is outdated and has a bug.

"devDependencies": {
  "swagger-snippet": "https://github.com/ErikWittern/swagger-snippet",
}

npm outdated --json --save false reports

{
  "swagger-snippet": {
    "current": "0.6.0",
    "wanted": "git",
    "latest": "git",
    "location": "node_modules\\swagger-snippet"
  }
}

The documentation (https://docs.npmjs.com/cli/outdated.html) says:

Git dependencies will always be reinstalled, because of how they’re specified.

I think that's why they are always treated as outdated. Possible values of "latest" and "wanted" are "git", "linked" and "remote".

assert-outdated should not return with an error for such dependencies, otherwise it's not usable with such links.