merge: move almost all change/delete conflicts to resolve phase (BC) (API) We have finally laid all the groundwork to make this happen. The only change/delete conflicts that haven't been moved are .hgsubstate conflicts. Those are trickier to deal with and well outside the scope of this series. We add comprehensive testing not just for the initial selections but also for re-resolves and all possible dirstate transitions caused by merge tools. That testing managed to shake out several bugs in the way we were handling dirstate transitions. The other test changes are because we now treat change/delete conflicts as proper merges, and increment the 'merged' counter rather than the 'updated' counter. I believe this is the right approach here. For third-party extensions, if they're interacting with filemerge code they might have to deal with an absentfilectx rather than a regular filectx. Still to come: - add a 'leave unresolved' option to merges - change the default for non-interactive change/delete conflicts to be 'leave unresolved' - add debug output to go alongside debug outputs for binary and symlink file merges