def METHOD_NAME(
    sourcegit_and_remote,
    distgit_and_remote,
    mock_remote_functionality_sourcegit,
    api_instance_update_source_git,
) -> PackitAPI:
    """Fixture returning an API instance where dist-git and source-git
    repos contain commits with git-trailers. The latest trailing commit
    is dist-git update (From-source-git trailer)."""
    sourcegit, _ = sourcegit_and_remote
    distgit, _ = distgit_and_remote
    (distgit / "file").write_text("foo")
    api_instance_update_source_git.dg.commit("add new file", "")
    api_instance_update_source_git.update_source_git("HEAD~..")
    mock_spec_download_remote_s(distgit)
    api_instance_update_source_git.sync_release(
        dist_git_branch="main",
        version="0.1.0",
        upstream_ref="0.1.0",
        mark_commit_origin=True,
    )
    return api_instance_update_source_git