updateInternalDependents incorrectly updates version of transitive devDependencies #947

Problem

updateInternalDependents currently incorrectly triggers version updates on packages with transitive dependencies on devDependencies. I appreciate that is too terse to make sense, a demo is clearer:

The following demonstration with reproduction steps is available at https://github.com/BPScott/changesets-transitive-deps-bug

Consider a repository with 3 packages:

• package-a
• package-b - this has a devDependency on package-a
• package-c - this has a runtime dependency on package-b

package-a is the only package with a changeset associated with it.

Expected behaviour

When running npm run changset version, I would expect changsets to:

• Update package-a: Increase the version in the package.json and generate a CHANGELOG entry, as there is a changeset associated with this package.
• Update package-b: Update the devDependency version of package-a to the new version i the package.json. The version of package-b should be untouched as only a devDependency changed. No CHANGELOG entry is created as the version does not change.
• Not touch package-c's package.json. Because package-b's version was not updated there should be no change to package-c's package.json or CHANGELOG.

Actual Behaviour

The expected changes to package-a and package-b's both occur as expected.

However modifications are made to package-c, when there should be none, because there package-b did not receive a version bump.

package-c's version number is increased in the package.json. A changelog heading for the new version is generated, but no content is present.

Proposed solution

Changsets is currently smart enough to skip bumping the version of a package is when one of its devDependencies has changed. Because that package does not recieve a version bump, neither should any of its dependencies. I.e. in the above example - because package-b did not receive a version bump, then package-c should be have a version bump either.