Function perform 

pub fn perform(
    target: &Path,
    choices: &NewChoices,
    plan_digest: &str,
    via: Via,
    state: &Path,
    options: &RunOptions,
) -> CommandResult

Creates the project: the plan recomputed and compared with the one the person confirmed (plan_digest), each step run in order (a step whose effect is already there is skipped), init in process, one commit as the person, the creation record, project.created.