changesets-renovate includes private (not published) packages

[moltar]

Describe the bug

The script that generates the changeset manifest will include a private package in the list.

Changesets will then fail to run with:

🦋 error Error: "renovate-c2f96a3" changeset mentions a release for a package "@foo/bar" but such a package could not be found.

To Reproduce

1. Touch a private file.
2. Run the script.
3. Observe that Markdown changeset includes the private package

Expected behavior

Do not include private packates.

Screenshots

N/A

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context

This can often happen in a monorepo context, where the root packages (monorepo root) receives an updated dependency.