hs3 → histfactory Relation

File in roofit/hs3	Includes file in roofit/histfactory
src / JSONFactories_HistFactory.cxx	inc / RooStats / HistFactory / Detail / HistFactoryImpl.h
src / JSONFactories_HistFactory.cxx	inc / RooStats / HistFactory / ParamHistFunc.h
src / JSONFactories_HistFactory.cxx	inc / RooStats / HistFactory / PiecewiseInterpolation.h
src / JSONFactories_HistFactory.cxx	inc / RooStats / HistFactory / FlexibleInterpVar.h