-- the path is an exploration of the tree which contains
-- the connexions and their reverses.
-- if the tree of connexions is
- -- A
- -- / \
- -- B E
- -- / \ \
- -- C D F
+ -- A
+ -- / |
+ -- B E
+ -- / | |
+ -- C D F
--
-- the path is A->B, B->C, C->B, B->D, D->B, B->A, A->E,
-- E->F, F->E, E->A.