Allow extract_release_notes_for_version to return the extracted release notes without saving to a file

[AliSoftware]

What does it do?

As it says on the tin.

The old implementation kinda had half-support for the case where we didn't provide a destination file path, but printed the result using puts instead of returning it as a value of the action.

Why?

This change will be useful in particular for my work on PocketCasts automation, as when automating the submission to TestFlight and creating the GitHub Release for beta builds, the PocketCasts team wants to always use the latest release notes extracted from CHANGELOG.md when submitting to external testers in TestFlight or creating the GH Release (since they might have added some new entries to the CHANGELOG.md as part of landing some bugfixes during the beta phase and want to include those as well).

This means we can't really rely on just reading the content of the release_notes.txt file that was previously extracted as part of code_freeze, as that file won't include the latest changes at the time we do a new beta. But we don't need to save the re-extracted content into the release_notes.txt file and re-commit the changes again at those stages, so calling the action without a extracted_notes_file_path: parameter and just manipulating the returned string would be better for those use cases.

Testing

I've tested this by pointing PocketCasts-iOS's Gemfile to my local copy of release-toolkit that contained this change and calling extract_release_notes_for_version without an extracted_notes_file_path: parameter and UI.message-printing the returned value.

Checklist before requesting a review

• Run bundle exec rubocop to test for code style violations and recommendations
• Add Unit Tests (aka specs/*_spec.rb) if applicable
• Run bundle exec rspec to run the whole test suite and ensure all your tests pass
• Make sure you added an entry in the CHANGELOG.md file to describe your changes under the appropriate existing ### subsection of the existing ## Trunk section.
• If applicable, add an entry in the MIGRATION.md file to describe how the changes will affect the migration from the previous major version and what the clients will need to change and consider.

[iangmaia]

👍