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.