rust: Add a Filelog struct that wraps Revlog Some filelog-specific logic is moved from code `rhg cat` into this struct where it can better be reused. Additionally, a missing end delimiter for metadata causes an error to be returned instead of being silently ignored. Differential Revision: https://phab.mercurial-scm.org/D11408

pub mod dirstate_map;
pub mod dispatch;
pub mod on_disk;
pub mod owning;
mod owning_dispatch;
pub mod path_with_basename;
pub mod status;