https://www.jenkins.io/doc/developer/extensions/git-client/ shows the extension point defined by the git client plugin and shows that it has no Javadoc. Since the extension point is intended to be used by others, it should have a Javadoc description that explains its purpose.

Refer to https://www.jenkins.io/doc/developer/extensions/credentials/ and https://www.jenkins.io/doc/developer/extensions/git/ for examples of plugins that define extension points and provide Javadoc comments describing the extension point.