commit: pass mergestate into _filecommit() instead of re-reading it...
commit: pass mergestate into _filecommit() instead of re-reading it
mergestate reading although cheap is not free. Let's read mergestate once on top
and pass it into `_filecommit()`.
In upcoming patches, we will be reading mergestate more in `_filecommit()`.
Differential Revision:
https://phab.mercurial-scm.org/D8984