changelog: drop the side_write argument to revlog splitting The only user is now gone.

changelog: stop useless enforcing split at the end of transaction Changelogs are no longer created inline, and existing changelogs are automatically split. Since we now enforce splitting at the start of any write, we don't need to enforce splitting at the end of the transaction. This has the nice side effect of killing the only user of "side_write".

branching: merge stable into default