From https://github.com/jenkinsci/google-play-android-publisher-plugin/pull/26:

When trackName variable is missing or misspelled, setting default trackName to production has an unwanted effect [i.e. accidentally publishing to production instead of internal]

Yeah, I would guess that a large proportion of users don't publish directly to production (i.e. they upload to alpha/beta/internal), and having this plugin default to production in the absence of explicit configuration, probably isn't the safest of defaults to have.

Let's:

• implement the breaking change of making trackName mandatory
• double-check what happens when an empty string (as opposed to a null value) in the rolloutPercentage is given — defaulting to 100% is possibly still reasonable here…