rust: Add a Filelog struct that wraps Revlog...
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
