Avoid trivial (u=u) constraints in AcyclicGraph.constraints_for
Avoid trivial (u=u) constraints in AcyclicGraph.constraints_for

Not sure how often this happens in practice but it seems it could.

Zimmi48/coq,ejgallego/coq,gares/coq,coq/coq,Matafou/coq,SkySkimmer/coq,Zimmi48/coq,JasonGross/coq,gares/coq,silene/coq,JasonGross/coq,JasonGross/coq,gares/coq,gares/coq,SkySkimmer/coq,gares/coq,SkySkimmer/coq,Matafou/coq,coq/coq,coq/coq,Zimmi48/coq,silene/coq,JasonGross/coq,ejgallego/coq,Matafou/coq,SkySkimmer/coq,coq/coq,Zimmi48/coq,ejgallego/coq,ejgallego/coq,silene/coq