mergestate: make `_resolve()` do both preresolve and resolve This patch removes the `preresolve` argument from `_resolve()` and makes it do both the "preresolve" and "resolve" steps without the caller having to call it twice. Differential Revision: https://phab.mercurial-scm.org/D11856

mergestate: merge `preresolve()` into `resolve()` The separation between `preresolve()` and `resolve()` was something added for the "merge driver" feature. Since we removed that in 32ce4cbaec4b (mergedriver: delete it, 2020-09-17), we don't need the separation anymore. More cleanups will follow. Differential Revision: https://phab.mercurial-scm.org/D11855

tests: remove unnecessary explicit args from `failfilemerge.py` The `failfilemerge()` function always raises an exception without looking at its arguments, so let's use `*args` and `**kwargs`. Differential Revision: https://phab.mercurial-scm.org/D11854

simplemerge: set `conflicts` earlier for :union tool Differential Revision: https://phab.mercurial-scm.org/D11853

downgrade: don't assume existence of nodemap files when downgrading Persistent nodemap files might not exist on a fresh repository, so ignore the potential missing file errors. Differential Revision: https://phab.mercurial-scm.org/D11806

typo: s/unkown/unknown across the codebase Differential Revision: https://phab.mercurial-scm.org/D11807

rhg: Update the dirstate on disk after status Differential Revision: https://phab.mercurial-scm.org/D11840

rhg: Add Repo::write_dirstate This method is not used yet. It saves to disk any mutation that was done to the `Repo`’s dirstate through `Repo::dirstate_map_mut`. It takes care of dirstate-v1 v.s. dirstate-v2, dockets, data files, appending when possible, etc. Differential Revision: https://phab.mercurial-scm.org/D11839

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

rhg: Make Repo::dirstate_parents a LazyCell Unify with the same abstraction used for other lazily-initialized components Differential Revision: https://phab.mercurial-scm.org/D11837