evolve: store the evolvestate file when encountering conflicts This patch makes `hg evolve` store the evolvestate file when it encounters merge conflicts while resolving content-divergence.

evolve: take out logic to complete phase-divergence in separate fn This patch takes out the logic to complete the content-divergence resolution to it's own separate function so that we can reuse it in case of interrupted resolution.

evolve: store divergent nodes in evolvestate when resolving content-divergence We need to store the divergent nodes in evolvestate so that we can continue an interrupted phase divergence resolution.

branching: merge stable into default