evolve: clean merge state when content divergence resolution has no changes This patch backs out b723805d7fe1, which only hid the problem. Usually mergestate is cleared (or should be cleared) when creating a new changeset, but sometimes there are situations when there's nothing to commit. When solving content divergence resulted in no changes and no new changesets were created, mergestate was left untouched. That's a problem because sometimes mergestate contains files with conflicts that were already resolved by user, and such mergestate only applies to the current wdir parent. Since evolve has already dealt with the current wdir parent successfully when it reached this code, this is a good place to clean the mergestate.