[Cleanup] Rename: TrivialFunction -> ZeroFunction

dune/tectonic/frictionpotential.hh

@@ -102,7 +102,7 @@ class RegularisedRateState : public FrictionPotential {
   double Vmin;
 };
 
-class TrivialFunction : public FrictionPotential {
+class ZeroFunction : public FrictionPotential {
 public:
   double evaluate(double) const { return 0; }
 

dune/tectonic/globalratestatefriction.hh

@@ -29,8 +29,8 @@ class GlobalRateStateFriction : public GlobalFriction<Matrix, Vector> {
                           ScalarVector const &weights,
                           ScalarVector const &weightedNormalStress)
       : restrictions(weightedNormalStress.size()) {
-    auto trivialNonlinearity =
-        std::make_shared<Friction>(std::make_shared<TrivialFunction>());
+    auto zeroNonlinearity =
+        std::make_shared<Friction>(std::make_shared<ZeroFunction>());
 
     Dune::MultipleCodimMultipleGeomTypeMapper<
         GridView, Dune::MCMGVertexLayout> const vertexMapper(gridView);
@@ -39,7 +39,7 @@ class GlobalRateStateFriction : public GlobalFriction<Matrix, Vector> {
       auto const i = vertexMapper.index(*it);
       auto const coordinate = it->geometry().corner(0);
       if (not frictionalBoundary.containsVertex(i)) {
-        restrictions[i] = trivialNonlinearity;
+        restrictions[i] = zeroNonlinearity;
         continue;
       }
       auto const fp = std::make_shared<ScalarFriction>(