Add a commandline argument to override the cache directory

src/engine/openspaceengine.cpp

@@ -112,6 +112,7 @@ namespace {
         std::string configurationName;
         std::string sgctConfigurationName;
         std::string sceneName;
+        std::string cacheFolder;
     } commandlineArgumentPlaceholders;
 }
 
@@ -283,6 +284,14 @@ bool OpenSpaceEngine::create(int argc, char** argv,
         return false;
     }
 
+    if (!commandlineArgumentPlaceholders.cacheFolder.empty()) {
+        FileSys.registerPathToken(
+            "${CACHE}",
+            commandlineArgumentPlaceholders.cacheFolder,
+            ghoul::filesystem::FileSystem::Override::Yes
+        );
+    }
+
     // Initialize the requested logs from the configuration file
     _engine->configureLogging();
 
@@ -599,6 +608,14 @@ bool OpenSpaceEngine::gatherCommandlineArguments() {
         "the scene file, overriding the value set in the OpenSpace configuration file"
     ));
 
+    commandlineArgumentPlaceholders.cacheFolder = "";
+    _commandlineParser->addCommand(std::make_unique<SingleCommand<std::string>>(
+        &commandlineArgumentPlaceholders.cacheFolder, "-cacheDir", "", "Provides the "
+        "path to a cache file, overriding the value set in the OpenSpace configuration "
+        "file"
+    ));
+    
+
     return true;
 }