changelog: change the implementation of `_divertopener`...
changelog: change the implementation of `_divertopener`
During a transaction, new data to the changelog index are "diverted". The
previous implementat ways pretty basic, we need something better to be able to
use the changelog vfs fully during transaction. (eg: accessing the vfs options).
Differential Revision:
https://phab.mercurial-scm.org/D8185