fix(gatsby-dev-cli): resolve correct versions of packages with unpkg

[vladar]

Description

This PR fixes an issue with the incorrect detection of changed dependencies in the case when local dependencies are not installed.

Say we have this in project package.json and dependencies are not installed (so no node_modules folder):

"dependencies": {
  "gatsby": "next"
}

In this case gatsby-dev-cli attempts to load package details from unpkg to compare against dependencies in the monorepo:

gatsby/packages/gatsby-dev-cli/src/utils/check-deps-changes.js

Lines 56 to 65 in 357230d

	// if package is not installed, we will do http GET request to
	// unkpg to check if dependency in package published in public
	// npm repository are different
	// this allow us to not publish to local repository
	// and save some time/work
	try {
	const response = await got(
	`https://unpkg.com/${packageName}/package.json`
	)

The problem is that packageName here will be gatsby and not gatsby@next. So it will always diff with dependencies of the latest version, regardless of the actual local version.

[pieh]

gatsby/packages/gatsby-dev-cli/src/local-npm-registry/publish-package.js

Line 42 in 54d4721

monorepoPKGjson.version = `${monorepoPKGjson.version}-dev-${versionPostFix}`

gatsby-dev might set to some version available only locally, so this unpkg would likely fail for those and fallback to using verdaccio which is fine I think?

[vladar]

This codepath is only active a) for the initial scan b) when there are no local dependencies (so no node_modules). If you have deps already installed with verdaccio, we won't even try to check unpkg.

So I think it should be fine