`append_backfilled`'s paragraph sat on top of `apply_backfill_states`, whose own doc ran on underneath it, so the function it described had none. The other was a half-sentence orphaned above a test in `labels.rs` — the opening of a section whose separator went to `sources.rs` and reads without it. Change-Id: I585e999c621c7945bc61f67f4213f3ff4eef2272