The error message used to only contain the last key of the merge failure
this commit changes the message to contain the full path to the merge
conflict, resolving ambiguity
Change-Id: I9848a559b1b888e50a548eef8609bf34506040de
The current `RelativeTo` design is both more complex and more confusing
than necessary. Its four variants are now reduced to only two. They are
now also represented as different classes, to better communicate the
difference in semantics and also intent.
Change-Id: Ia60fc7a2dfa0f62bdef90dde347fd8603fd3fbf9