Goal:
  
  G1 : t
  G2 : t
  H : invariants G1
  H0 : invariants G2
  H1 : acyclic_no_loop G2
  hsub : subgraph G1 G2
  acG1 : acyclic_no_loop G1
  x : VSet.elt
  y : VSet.elt
  hx : VSet.In x (border_set G1 (EdgeSet.diff (E G2) (E G1)))
  hy : VSet.In y (border_set G1 (EdgeSet.diff (E G2) (E G1)))
  ============================
   ((lsp G1 x y == lsp G2 x y) = true -> (lsp G2 x y <= lsp G1 x y)%nbar)


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrmove@1> $1 $2