We often need Jenkins jobs to test whether a compose has a particular build or not. These jobs will kick off a new compose if the latest one does not have the build in question.

This helps with CI cases where a lot of builds are getting tagged in quick succession, and we want to continuously compose them as soon as possible, but only generate the minimum number of composes.

Currently we do this in a Jenkins job by scraping the compose's productmd JSON with jq. It would be great to extract this into a small "compose-has-build" utility.

compose-has-build [-q] <compose-path> <nvr>

prints "compose <id> has build <nvr>" and exits with 0
prints "compose <id> does not have build <nvr>" and exits with 1

Note: Brew's messages on VirtualTopic.eng.brew.build.tag have an nvr field that does not contain the epoch. In other words, compose-has-build should not expect the epoch.