Function ensure_changed_files_represented 

pub fn ensure_changed_files_represented(
    selected: &mut Vec<Fragment>,
    all_fragments: &[Fragment],
    changed_files: &[PathBuf],
    remaining_budget: u32,
    root_dir: &Path,
    preferred_revs: &[String],
    batch_reader: Option<&mut CatFileBatch>,
    core_ids: &FxHashSet<FragmentId>,
)