Function compare_candidates 

pub async fn compare_candidates(
    pool: &PgPool,
    actor: &Actor,
    file_id: Uuid,
    shown_sha256: &str,
) -> AppResult<Vec<CompareCandidate>>

The models a file version can be compared with, newest revision and version first (at most 50; versions with the same content as shown are left out). The file’s item is readable, so are its other revisions.