Allow atmosphere on reconstructed state, remove RelEuler system

src/Evolution/DiscontinuousGalerkin/CMakeLists.txt

@@ -14,6 +14,7 @@ spectre_target_headers(
   MortarDataHolder.hpp
   MortarTags.hpp
   NormalVectorTags.hpp
+  TimeDerivativeDecisions.hpp
   UsingSubcell.hpp
   )
 

src/Evolution/DiscontinuousGalerkin/TimeDerivativeDecisions.hpp

@@ -0,0 +1,18 @@
+// Distributed under the MIT License.
+// See LICENSE.txt for details.
+
+#pragma once
+
+namespace evolution::dg {
+/*!
+ * \brief Runtime control over time derivative work done.
+ *
+ * - `compute_flux_divergence`: if `true` then we compute and add the flux
+     divergence to the volume time derivative. Set to `false` to elide work
+     where you know the solution is spatially constant.
+ */
+template <size_t Dim>
+struct TimeDerivativeDecisions {
+  bool compute_flux_divergence = true;
+};
+}  // namespace evolution::dg

src/Evolution/Executables/CMakeLists.txt

@@ -9,7 +9,6 @@ add_subdirectory(GeneralizedHarmonic)
 add_subdirectory(GrMhd)
 add_subdirectory(NewtonianEuler)
 add_subdirectory(RadiationTransport)
-add_subdirectory(RelativisticEuler)
 add_subdirectory(ScalarAdvection)
 add_subdirectory(ScalarTensor)
 add_subdirectory(ScalarWave)