Branch filtering

A module can now find out which branch it runs on, and whether that branch is in the main branch of the repository. A pipeline can then do different work for each case. For example, it deploys to production from the main branch, and to a preview environment from a pull request.

New Git APIs give modules the information that they need:

• GitRepository.remotes and GitRepository.remote list the remotes of a repository.
• GitRepository.defaultRemote returns the default remote: the only remote, or origin, or the remote of the current branch.
• GitRef.contains tells if a commit is in the history of a ref. It works for branches, tags and commits, also from a detached HEAD in CI.

The APIs use only Git concepts. They work with trunk development, and also with other workflows.