rhg: Add lazy/cached dirstate data file ID parsing on Repo...
rhg: Add lazy/cached dirstate data file ID parsing on Repo
The `dirstate_parents`, `dirstate_data_file_uuid`, and `dirstate_map` members
of `Repo` can be access in any order and the `.hg/dirstate` file should only
be opened once.
Differential Revision:
https://phab.mercurial-scm.org/D11838