A tree conflict currently reports whether the incoming change was a delete or add or modify. To help the user resolve the conflict, it would be better to also store and report the merge-left source and merge-right source URL@REV for a merge, and something similar for an update/switch. This would avoid the user having to remember or try to find out this info. In some cases, e.g. update a mixed-revision WC, I suspect (but have not verified) that it may presently be impossible to determine what the previous base revision number was after trying an update that caused tree conflicts.